Surgical time-outs are designed to promote situation awareness, teamwork, and error prevention. The pre-incision time-out in particular aims to facilitate shared mental models prior to incision. Objective, unbiased measures to confirm its effectiveness are lacking. We hypothesized that providers’ mental workload would reveal team psychophysiological mirroring during a formal, well-executed pre-incision time-out. Heart rate variability was collected during cardiac surgery cases from the surgeon, anesthesiologist, and perfusionist. Data were analyzed for six cases from patient arrival until sternal closure. Annotation of surgical phases was completed according to previously developed standardized process models of aortic valve replacement and coronary artery bypass graft procedures, producing thirteen total surgical phases. Statistical analysis revealed significant main effects. Tukey HSD post hoc tests revealed significant differences across provider roles within various phases, including Anesthesia Induction, Heparinization, Initiation of Bypass, Aortic Clamp and Cardioplegia, Anastomoses or Aortotomy, Separation from Bypass, and Sternal Closure. Despite these observed differences between providers over various surgical phases, the Pre-incision Time-out phase revealed almost negligible differences across roles. This preliminary work supports the utility of the pre-incision safety checklist to focus the attention of surgical team members and promote shared team mental models, measured via psychophysiological mirroring, using an objective mental workload measure. Future studies should investigate the relationship between psychophysiological mirroring among surgical team members and the effectiveness of the pre-incision time-out checklist. The cogDespite these findings, effectiveness of the pre-incision time-out has yet to be demonstrated via objective measures of mental states, such as mental workload (MWL). Though definitions of MWL often vary, it is generally accepted that individuals have limited cognitive and attentional capacity . MWL is To date, despite improvements in patient outcomes and perceived team dynamics attributed to surgical time-outs, there is a lack of objective evidence supporting their effectiveness. The aim of this study is to investigate the relationship between providers’ MWL and surgical phases within aortic valve replacement (AVR) and coronary artery bypass graft (CABG) surgeries at a tertiary academic hospital, with special interest in the pre-incision time-out phase. Given recent evidence suggesting that mirrored changes in team workload reflect the presence of shared team-wide mental models ,18, we h2The research protocol for this project was approved by the Institutional Review Boards of VA Boston Healthcare System and Harvard Medical School (IRB#3047). All individuals entering the operating room (OR) during recordings provided written informed consent prior to the start of the surgery.Data were collected during AVR and CABG procedures in the cardiac OR of a tertiary teaching hospital between January 2017 and November 2018. Data sources included two GoPro HERO4 Black Edition cameras  for video capture of 1) the entire OR and 2) the surgical field; three Sony ICD-PX440 audio recorders  for audio capture of 1) the attending surgeon, 2) the attending anesthesiologist, and 3) the primary perfusionist; and three Polar V800 chest straps with H10 sensors  for heart rate capture of 1) the attending surgeon, 2) the attending anesthesiologist, and 3) the primary perfusionist.For each case, all audio, video, and physiological recordings were manually time synced and integrated by one researcher (LKM). Data were analyzed from the time the patient was transferred onto the operating table until the end of sternal closure. Identification and annotation of surgical phases was done manually by one coder (LKM), according to previously developed standardized process models of AVR and CABG procedures . This prWithin HRV data collected, we are specifically interested in vagally-mediated measures of MWL, namely the root mean square of the successive differences (RMSSD) . VagallyStatistical analysis using SPSS version 26.0  included a mixed model ANOVA defining surgical phase as a within-subjects factor and provider role as a between-subjects factor. Tukey HSD post hoc comparisons were calculated in response to identification of significant main effects. Results are reported as  and are considered significant at the P<0.05 level.3Primary analysis of physiological data collected from three cardiac surgery team members  involved analysis of HRV components from six total cases . Participating clinicians included two surgeons, four anesthesiologists, and three perfusionists. Participant demographics can be found in Table 1Partial data are missing from various phases within some of these cases due to equipment malfunctioning, which is considered to be unrelated to participant characteristics. Data were transformed to replace missing values using the SPSS method of Linear Trend at a Point, resulting in 18 data points for each phase (3 providers x 6 cases). Using this method, missing values are replaced with their predicted values, based on a regression of the index variable scaled 1 to n . Due to ηp2=0.49) between provider HRV values within surgical phases. Post hoc analysis via Tukey HSD showed that during the Anesthesia Induction phase, anesthesiologists’ (14.36 ± 3.89) MWL was significantly higher than that of the perfusionists . During Heparinization, surgeons (11.00 ± 1.65) experienced significantly higher MWL compared to perfusionists . The same observation was observed within the Initiation of Bypass phase , the Aortic Clamp and Cardioplegia phase , the Anastomoses or Aortotomy phase , the Separation from Bypass phase , and the Sternal Closure phase . The differences in MWL between surgeons and anesthesiologists during the Aortic Clamp and Cardioplegia phase  as well as the Anastomoses/Aortotomy phase  were also significant.A mixed model ANOVA revealed significant differences =7.29, p<0.001, Despite significant differences across provider roles during multiple phases of the surgeries, the Pre-incision Time-out phase revealed almost negligible differences across the three roles (range: 2.47 ms), indicating a mirroring of team workload across individuals  while te4Evidence on human factors and teamwork has corroborated that avoidable peri-operative complications might stem from differing perceptions of effective communication, teamwork, and situational awareness by members of the cardiac surgical OR team  and thatRecent work by Brown and colleagues identified a lack of shared mental models within and between disciplines caring for cardiac surgical patients across most critical moments during surgery . Brown iThe introduction of objective measures of mental states represents another dimension of rigor to evaluate team dynamics, which has yet to be demonstrated or reported during the pre-incision time-out until now. HRV analysis is the most commonly utilized objective measure of MWL during surgery  and primThe lack of difference between providers’ HRV within the pre-incision time-out phase may suggest unbiased, objective evidence of shared mental models via psychophysiological mirroring. The lack of difference observed between providers’ HRV in the few remaining phases, including Pre-induction and Sterile Prepping could be reflective of the same mechanisms, but may also be influenced by the relative lack of surgical procedures occurring during these early stages, in combination with greater task engagement of the trainees relative to senior team members. Even during the Sternotomy phase, which marks the beginning of the surgical intervention and similarly revealed no significant differences in HRV across providers, it is often observed that the primary hands-on patient management and interaction is provided by the trainee, while the HRV data acquired through this study captured that of the senior attending team members.Within these data, HRV values of the cardiac surgery team demonstrate divergent dynamics, evidenced by differences in MWL across provider roles emerging over the course of the surgery. For example, while mirroring of mental states is observed during the pre-incision time-out phase, many remaining downstream phases show significant differences between MWL of at least two roles. During the surgical procedure, almost every phase relies on the three individual team members leveraging specialized skills to complete distinct tasks simultaneously, with a shared common goal held by the team. However, during the pre-incision time-out phase, these dynamics converge, which could be attributed to the team members’ efforts striving to complete not only the same overarching goal, but also the same task. Interleaved episodes of convergence and divergence is indicative of the evolution of adaptive physiological dynamics within the team .Interpretations from this preliminary study are limited by the small sample size and data transformation performed to replace missing data. Nonetheless, the findings observed hold promise for future work in measuring MWL during complex tasks, including surgery “in the wild”. Further, findings may be generalizable to other surgical and invasive settings which may be considered similarly complex.Future work will use objective HRV measures to investigate teams with high- versus low-convergence in MWL to determine potential determinants of psychophysiological synchrony and/or mirroring. The identification of factors contributing to high- versus low-convergence states may result in targeted training and prevention approaches, advancing the impact of cognitive engineering and human factors approaches to patient safety efforts . Implica


To the Editor,Persistent sciatic artery (PSA) is a rare vascular anomaly resulting from incomplete obliteration of the embryonic dorsal axial artery , 2. The When we performed pre-scanning of ultrasound-guided popliteal sciatic nerve block for a 67-year-old female patient who was going to undergo left total knee replacement, a hypoechoic round pulsating structure was identified between TN and CPN within the paraneural sheath at the popliteal fossa Fig. . It turnIn the present case, a presumed PSA was identified within the paraneural sheath at the bifurcation of TN and CPN, which is usually filled with loose connective tissue and is a target of local anesthetic injection during the ultrasound-guided popliteal sciatic nerve block . Conside


With the appearance of the worldwide AIDS pandemic four decades ago came a number of debilitating opportunistic infections in patients immunosuppressed by the pathogenic human retrovirus HIV. Among these was a severe sight-threatening retinal disease caused by human cytomegalovirus (HCMV) that remains today a significant cause of vision loss and blindness in untreated AIDS patients without access or sufficient response to combination antiretroviral therapy. Early investigations of AIDS-related HCMV retinitis quickly characterized its hallmark clinical features and unique histopathologic presentation but did not begin to identify the precise virologic and immunologic events that allow the onset and development of this retinal disease during HIV-induced immunosuppression. Toward this end, several mouse models of experimental cytomegalovirus retinitis have been developed to provide new insights into the pathophysiology of HCMV retinitis during AIDS. Herein, we provide a summary and comparison of these mouse models of AIDS-related HCMV retinitis with particular emphasis on one mouse model developed in our laboratory in which mice with a murine acquired immunodeficiency syndrome (MAIDS) of murine retrovirus origin develops a reproducible and well characterized retinitis following intraocular infection with murine cytomegalovirus (MCMV). The MAIDS model of MCMV retinitis has advanced the discovery of many clinically relevant virologic and immunologic mechanisms of virus-induced retinal tissue destruction that are discussed and summarized in this review. These findings may extend to the pathogenesis of AIDS-related HCMV retinitis and other AIDS-related opportunistic virus infections. HIV is a pathogenic human retrovirus that causes unique immunosuppression characterized by a progressive deterioration of immune functions that culminates in the clinical condition known as AIDS ,2. A cenAIDS-related HCMV retinitis initially caused vision loss and blindness in ~30% of AIDS patients either unilaterally or bilaterally prior to the therapeutic use of combination antiretroviral therapy (ART) ,13,14. TFour decades after the appearance of AIDS in our society, and the recognition of AIDS-related HCMV retinitis worldwide, a large knowledge base has been established that defines with clarity its clinical and histopathologic presentations ,18,19. TCytomegaloviruses are highly species-specific ,21. ThusEarly attempts to create an animal model for HCMV retinitis using immunologically normal mice of various strains were largely unsuccessful with detection of only MCMV antigens and/or MCMV DNA within various ocular tissues following anterior chamber or intravitreal virus inoculation but without development of retinitis ,25,26. HA more reproducible experimental mouse model of HCMV retinitis in immunocompromised humans was later developed by Atherton, Cousins, and coworkers ,29 that In an attempt to create a more clinically relevant mouse model of AIDS-related HCMV retinitis, we employed C57BL/6 mice with murine acquired immunodeficiency syndrome (MAIDS) that develops within 1 to 3 weeks following systemic infection with the murine retrovirus mixture, LP-BM5 ,38,39. TBuilding on the early development and comprehensive characterization of MAIDS by Morse and colleagues ,38,39, wSeveral insights into the pathogenesis of MAIDS-related MCMV retinitis have been discerned by us using this experimental mouse model of AIDS-related HCMV retinitis, some predicted, yet many others unexpected, as summarized below. The reader is also directed to other reviews of the MAIDS model of MCMV retinitis for more detailed information ,14,38,42Like many animal viruses, cytomegaloviruses induce a number of host cell changes during productive replication that lead to cell injury or cell death and thereby contribute to tissue pathology and the appearance of clinical disease. That virus replication and cytopathology contribute to the onset and development of retinal tissue destruction during the pathogenesis of AIDS-related HCMV retinitis has been recognized for many years. Evidence for direct virus infection of the retinal tissues of the eyes of AIDS patients with HCMV retinitis include the detection of HCMV-encoded nucleic acids and proteins, the detection of virus-induced inclusions within various retinal cells, and the appearance of pathognomonic cytomegalic cells within areas of retinal necrosis ,29. ThesAdditional studies by us, however, discovered that the MCMV-infected eyes of mice who are at an intermediate stage of MAIDS development, i.e., 4 weeks after retrovirus infection (MAIDS-4 mice), are resistant to retinitis development despite harboring high amounts of infectious virus  and at amounts equivalent to that found within the MCMV-infected eyes of retinitis-susceptible MAIDS-10 mice ,43. ThisBecause seropositivity to HCMV is ~80% worldwide ,6 and imSignificant loss of cellular immunity and the concomitant appearance of opportunistic pathogens is a hallmark of AIDS development . The appgld mice). Upon subretinal MCMV inoculation of groups of PKO mice, gld mice, MAIDS mice, or immunocompetent mice, a clear difference in resistance or susceptibility to MCMV retinitis development was observed among the animal groups. Whereas mice without MAIDS but deficient in the Fas/FasL cytotoxic pathway showed absolute (0%) resistance to MCMV retinitis as observed for healthy mice who were immunocompetent, mice without MAIDS but deficient in the perforin cytotoxic pathway showed significant susceptibility to MCMV retinitis at a frequency of >90% and at a level equivalent to that observed for mice with MAIDS [gld mice when transferred to recipient PKO mice significantly reduced susceptibility to MCMV retinitis following challenge by subretinal MCMV inoculation. In sharp contrast, splenic immune cells from donor MCMV-immunized PKO mice when transferred into recipient PKO mice failed to protect against MCMV retinitis upon challenge. Cytotoxic CD8+ T cells as a cellular component of adaptive immunity kills virus-infected cells via distinct pathways of cytolysis that include the perforin cytotoxic pathway and the Fas/Fas cytotoxic ligand pathway ,51. Becath MAIDS ,51. Adopth MAIDS ,55. SpleThe finding that loss of the perforin cytotoxic pathway, but not loss of the Fas/FasL cytotoxic pathway, imparts susceptibility to MCMV retinitis in mice without MAIDS prompted us to hypothesize that mice with MAIDS are susceptible to MCMV retinitis due to loss of the perforin cytotoxic pathway. This hypothesis was tested by comparing perforin mRNA levels of splenic T cells and MCMV-infected eyes collected from mice with MAIDS with perforin mRNA levels of splenic T cells and MCMV-infected eyes collected from healthy mice. In support of this hypothesis, perforin mRNA levels were dramatically reduced within splenic T cells and MCMV-infected eyes of retinitis-susceptible MAIDS mice when compared with retinitis-resistant healthy mice who showed consistently high amounts of perforin mRNA production within splenic T cells and MCMV-infected eyes ,55. That suppression of the perforin cytotoxic pathway during retrovirus-induced immunosuppression might represent a major mechanism by which mice with MAIDS become susceptible to onset of MCMV retinitis was explored further using a cytokine immunotherapy approach. Reasoning that both HIV-infected humans and LP-BM5-infected mice exhibit a profound systemic shift in cytokine production from a Th1 profile to a Th2 profile during progression of AIDS and MAIDS, respectively ,57, we pHaving shown that loss of the perforin cytotoxic pathway results in susceptibility to MCMV retinitis  and thatWe therefore conclude that cellular immunity is far more important that humoral immunity in protecting immunocompetent mice from developing MCMV retinitis. Not only do cytotoxic CD8+ T cells play a prominent role in this protection, but it is the perforin cytotoxic pathway and not the Fas/FasL cytotoxic pathway of cellular immunity that is needed for protection. The perforin cytotoxic pathway appears to be lost in retinitis-susceptible mice with MAIDS but is restored by systemic IL-2 immunotherapy that results in renewed resistance to MCMV retinitis as seen in healthy mice. Whether dampening of the perforin cytotoxic pathway utilized by cellular immunity contributes to increased susceptibility to HCMV retinitis during AIDS remains to be determined. If true, measurement of perforin-mediated cytotoxicity might be a better quantification of cellular immunity than measurement of total CD4+ and/or CD8+ T cells as a predictor for risk of development of HCMV retinitis in various immunosuppressed patient populations including patients with AIDS . Our studies exploring cytokine immunotherapy with IL-2 or IL-12 encouraged additional investigations to learn more about the possible contributions of individual cytokines toward the pathophysiology of MAIDS-related MCMV retinitis. Initial studies focused on tumor necrosis factor alpha (TNF-a) and interferon gamma (IFN-g) because TNF-a is a major proinflammatory cytokine often associated with tissue necrosis  and IFN-−/− mice) or IL-10 (IL-10 −/− mice) production showed equivalently high intraocular amounts of infectious virus as well as equivalent susceptibility to MCMV retinitis when compared with wildtype mice with MAIDS [Additional studies were directed at IL-4 and IL-10, two major Th2 cytokines shown to increase systemically during the progression of HIV infection to AIDS as part of the Th1/Th2 cytokine shift . Having th MAIDS . These f−/− mice with late-stage MAIDS exhibit partial restoration of IL-17 production in spleens or eyes following systemic or subretinal MCMV infection, respectively [IL-17 is another proinflammatory cytokine. Produced by CD4+ Th17 cells, this cytokine has been associated with several diseases of the eye including those of autoimmune origin . Initialectively . Alarmins are immune activating cytokines that are released from damaged cells. One such alarmin, IL-1a, functions early in the pathogenic process to induce inflammation via recruitment of macrophages and neutrophils. We therefore predicted that the MCMV-infected eyes of mice with MAIDS would show significant intraocular stimulation of IL-1a because macrophages and neutrophils are a prominent feature of the inflammation that develops during the pathogenesis of MAIDS-related MCMV retinitis (and AIDS-related HCMV retinitis). As predicted, retinitis-susceptible MCMV-infected eyes of MAIDS mice at 3 days after intraocular infection showed dramatic increases in IL-1a mRNA and protein amounts when compared with retinitis-resistant MCMV-infected eyes of healthy mice that showed minimal IL-1a production . By compSuppressor of cytokine signaling (SOCS) proteins are inducible negative regulators of cytokine signaling pathways ,71. SOCSInitial studies revealed that SOCS1 and SOCS3 (but not SOCS5) mRNA and protein were remarkably stimulated within the MCMV-infected eyes of MAIDS-10 mice during retinitis development . In compAdditional studies were performed using an in vitro cell culture approach to define with greater clarity the production of SOCS1 and SOCS3 during the course of MCMV replication. Because macrophages contribute prominently to the inflammation observed during cytomegalovirus retinitis  and macrCollectively, the accumulated findings for SOCS1 and/or SOCS3 so far suggest that they may affect the severity of cytomegalovirus disease differentially in a cell-type-specific manner within the ocular compartment. It remains unclear, however, whether virus-induced stimulation of SOCS1 and/or SOCS3 is protective or pathogenic in the eye during MAIDS-related MCMV retinitis, an uncertainty that continues to motivate further investigations of SOCS and cytomegalovirus retinitis pathogenesis. Indeed, these host proteins are being recognized as possible therapeutic targets for cancers and other eye diseases and may therefore prove to be important for the future treatment of AIDS-related HCMV retinitis or other herpesvirus diseases . Clearly, virus replication within retinal cells and the associated cytopathology contribute directly to retinal cell death during the onset and development of the necrosis that helps to define the unique retinal tissue pathology associated with AIDS-related HCMV retinitis. Not every retinal cell exhibits cytopathological changes, however, suggesting that other mechanisms of cell death may operate. One distinct possibility is the operation of programmed cell death pathways that serve to limit virus spread and confine pathology as part of the host’s innate immune responses against virus infection. Multiple cell death pathways have been recognized. We are therefore performing a series of investigations to determine the relative contributions, if any, of several individual cell death pathways toward retinal tissue destruction during the evolution of MAIDS-related MCMV retinitis. Those cell death pathways investigated to date include apoptosis, pyroptosis, necroptosis, and parthanatos .Recognized in 1972, apoptosis is probably the best studied of the cell death pathways, especially with respect to virus infections . The mec−/− MAIDS mice, GSDMD −/− MAIDS mice, or IL-18 −/− MAIDS mice developed full-thickness retinal necrosis. Instead, these animals exhibited an atypical pattern of retinal disease characterized by thickening and proliferation of the RPE layer with relative sparing of the neurosensory retina [Pyroptosis is a more recently recognized caspase-dependent cell death pathway  that is y retina . SurprisMore recent investigations have focused on two additional programmed cell death pathways, necroptosis  and partResults of the many investigations summarized above underscore the unexpected complexity of the immunopathology of MAIDS-related MCMV retinitis that in many respects mirrors the complexity of retrovirus-induced immunopathology during the evolution of MAIDS in mice that also extends to AIDS in humans. With this in mind, we embarked on a new direction of investigation designed to assess in a more comprehensive manner the intraocular pattern of immune response gene expression within MCMV-infected eyes during health and disease. This was accomplished using NanoString nCounter technology that allows for the direct measurement of the transcription of hundreds of genes simultaneously and without the need for amplification . We therA number of clinically relevant mouse models of MCMV retinitis have been developed over the years that differ with respect to the method by which immunosuppression is achieved and with differing strengths and weaknesses . NonetheThese findings bring particular attention to those events working either separately or in concert that could be exploited as new therapeutic approaches for the management of AIDS-related HCMV retinitis in the clinical setting. These findings might also extend to retinal diseases caused by other human herpesviruses in both immunologically normal persons and retrovirus-immunosuppressed patients.


Introduction: We conducted a cumulative environmental health risk assessment of whether specialty vape shops and poor air quality are more likely to co-occur in socially disadvantaged neighborhoods where racial/ethnic minority youth live.Methods: We examined the population-adjusted incidence of specialty vape shops in relation to youth race/ethnicity, neighborhood socioeconomic status (SES), and air quality (nitrogen dioxide [NO2]) at the census tract level across the conterminous United States for 2018.Results: We did not find disparity in vape shop incidence related to minority youth race/ethnicity. Vape shop incidence was significantly negatively associated with all the youth race/ethnicities examined. The two lowest SES quintiles had nearly double the rate of specialty vape shop incidence compared with the highest SES quintile. Specialty vape shop incidence increased with NO2 concentration, with more vape shops in poor air quality neighborhoods.Conclusions: Specialty vape shops are disproportionately present in neighborhoods with poor air quality and where socially disadvantaged youth live. The increased incidence of vape shops in poor air quality neighborhoods, particularly in an urban context with increased traffic emissions, further points to potentially disproportionate impacts on disadvantaged populations due to cumulative social and environmental risks. This raises environmental justice and health equity concerns. Retailer-focused strategies aimed at limiting youth exposure to electronic cigarettes' labeling and advertising, preventing sales to minors, and limiting the number of retailers in low-SES neighborhoods may reduce initiation and help prevent tobacco-related health disparities among youth. Cumulative exposure to environmental hazards may cause greater harm to health than would likely occur in the absence of those vulnerabilities.14Of concern is that low-SES communities in the United States, particularly children and the elderly, are also disproportionately exposed to environmental hazards and their health impacts.15 and other socioecological approaches16 may be particularly useful for understanding and addressing tobacco-related health disparities. Such approaches aid in identifying both the root causes of tobacco-related health disparities and the populations that are concurrently exposed to multiple social and environmental hazards.14Tobacco-related health disparities are a function of the interplay of individual, physical, and social factors. Therefore, cumulative risk assessments17 For traditional tobacco products, studies suggest that retailers are more numerous and more dense in racial/ethnic minority and low-SES communities and are broadly associated with disparities in exposure to tobacco marketing, tobacco use, and tobacco-related diseases.18The role of the tobacco retail landscape in tobacco-related health disparities has received increased attention, including the opportunities it presents for tobacco control and eliminating disparities.19–21 Consistent with a trend over the past several years, data from the 2020 National Youth Tobacco Survey show that e-cigarette was the most commonly used tobacco product among youth attending school.22 Retailers specializing in tobacco products, such as vape shops, are among the most common sources of e-cigarettes for youth after social sources.24Recent studies also suggest that the retail landscape for electronic nicotine delivery systems , as with traditional tobacco retailers, poses environmental health risks to youth.20 Taken together, these studies suggest that vape shops are features of the built environment that can be a source of harm to health through youth exposure to tobacco product labeling and advertising. Therefore, vape shops are themselves associated with an environmental health risk to youth.E-cigarette retailer density and proximity are associated with higher exposure to e-cigarette advertisements and e-cigarette use among youth.25 and racial/ethnic minority neighborhoods.25 This is of concern as recent reports indicate that students from socially disadvantaged communities attending Title 1 schools (schools with high numbers or high percentages of students from low-income families) are susceptible to e-cigarette use.26Available national assessments report disproportionately higher density of vape shops in socially disadvantaged27 Among Hispanic youth, use prevalence was highest for e-cigarettes compared with other products. For non-Hispanic Black or African American youth, e-cigarette use prevalence (6.2%) is similar to use prevalence for cigars (6.5%), the tobacco product most commonly used by this population.22 These factors raise health concerns, given reports of respiratory symptoms in youth associated with e-cigarette use.28–30Hispanic high schoolers are more likely to be susceptible to e-cigarette use compared with their non-Hispanic counterparts.31These reports also raise environmental justice (EJ) concerns. Executive Order 12898 and the associated Council on Environmental Quality guidance direct federal agencies to identify and address EJ aspects of their activities. Following this, the Federal Interagency Working Group on EJ recommends that federal agencies consider the potential for environmental health hazards to disproportionately affect minority and low-income populations through the National Environmental Policy Act processes.32 Additionally, Executive Order 13045 encourages federal agencies to identify and assess environmental health and safety risks that may disproportionately affect children.Identifying and addressing disproportionately high and adverse human health and environmental effects on low-income populations and American Indian/Alaska Native communities are goals for the U.S. Department of Health and Human Services as part of strategic elements of EJ.13As nascent sources of exposure, vape shops are a feature of the built environment that can be a source of harm to health through exposure of youth to tobacco labeling and advertising, and e-cigarette retailers may contribute to the cumulative environmental health risks faced by low-SES and minority communities who already bear disproportionate impacts of tobacco-related health disparities.21Little evidence exists regarding whether vape shops contribute to the cumulative social and environmental risks experienced by low-SES and minority youth. Such EJ assessments of the vape shop retail landscape, in relation to marginalized populations and other co-occurring environmental hazards, may aid efforts tackling health disparities from tobacco use among youth.In this study, we used a place-based approach to examine the co-occurrence of two environmental health risks—specialty vape shops and poor air quality—as well as a social stressor (SES). We further examined whether these factors co-occur in places where youth who belong to racial/ethnic minority communities live. Specifically, we examined the statistical relationships of the presence of specialty vape shops with youth race/ethnicity, a composite SES indicator , and an ambient air quality indicator  at the census tract level across the conterminous United States.The study did not involve any human participants or personally identifiable information, and used secondary data collected from publicly available sources (e.g. Census bureau). Therefore, ethics approval and consent to participate were not applicable.33A restricted definition of vape shops is appropriate for an accurate assessment of the socioenvironmental correlates of specialty vape shops. Tobacco retailers carrying a variety of product types outnumber specialty vape shops. In addition, the association of traditional tobacco retailers with minority and low-income communities is well established. Hence, a restrictive definition, excluding establishments that sell tobacco products other than e-cigarettes, helps reduce the potentially confounding influence of tobacco retailers carrying varied tobacco products.21 We mapped the specialty vape shop location data from the study by Venugopal et al.21 to the 5-year estimates of the 2014–2018 American Community Survey geodatabase census tracts across the conterminous United States.We utilized the national specialty vape shop data and methods that were employed for identifying and locating 7475 specialty vape shops throughout the conterminous United States for 2018 .Racial/ethnic diversity is higher among youth, the population of interest examined in this study, compared with the overall U.S. population.We then compiled data on the number of persons below 18 years of age  by race/ethnicity of interest  and calculated the percentages in each census tract.36 The SES index is derived from seven variables .We used the composite SES index data available from the Surveillance, Epidemiology, and End Results census tract-level SES database.36 We obtained the census tract SES quintile data (2013–2017) and overlaid them with the vape shop counts and race/ethnicity data. Due to differences in SES composite index data availability at the census tract level, 102 of 7475 specialty vape shops (1.4%) in 2333 census tracts were excluded.The SES composite index is categorized in quintiles of equal population size, with the first quintile (Group 1) representing the lowest and the fifth quintile (Group 5) representing the highest SES.SES quintile data were integrated with vape shop counts and race/ethnicity data for 69,594 census tracts (2) as an environmental hazard indicator variable. NO2 is used as an overall indicator of air pollution and air quality, especially for traffic-related air pollutants.37 Long-term NO2 exposure is associated with increased incidence of pediatric asthma and respiratory infections.38We used nitrogen dioxide  at each U.S. census tract.We utilized a global, high spatial resolution (0.01°×0.01°), annual average, NOI test statistic with a first-order queen contiguity spatial weight matrix, defining the neighborhood structure of each census tract.At the census tract level, we generated summary statistics of youth race/ethnicity and socioenvironmental attributes by the number of specialty vape shops. We generated summary statistics for both the broader dataset of vape shop counts by census tracts and the dataset used for final analyses. We first examined spatial autocorrelation in vape shop counts per census tract using Global Moran's I value using a permutation test  and generated a spatial lag variable.We removed 17 census tracts without defined neighbors from the 69,594 tracts, one of which contained a single vape shop. We tested the statistical significance of Global Moran's 2 using a generalized linear mixed-effects model (GLMM). First, we ran multiple candidate models fitted using maximum likelihood and Laplace approximation. The candidate models contained vape shop count as a response variable; race/ethnicity, SES, and NO2 as predictor variables; natural log of census tract population as an offset variable; and spatial lag variable as a random effect to account for potential spatial autocorrelation.We analyzed the statistical association of vape shop counts in the remaining 69,577 census tracts with youth race/ethnicity, SES, and median NORace/ethnicity data on White alone, Hispanic, or Latino youth were excluded from the analysis given the focus on examining census tract-level vape shop density associations with proportions of minority youth and to avoid multicollinearity. We ran Poisson, negative binomial, zero-inflated Poisson, zero-inflated negative binomial, and truncated Poisson hurdle or truncated negative binomial hurdle GLMMs, all with log link functions. We then selected the best-fit and parsimonious model based on the combination of Akaike information criteria and Bayesian information criteria, with lower values indicating better fit.χ2 tests to determine the statistical significance of the predictors in the selected model. We ran post hoc comparisons among SES quintiles using Dunnett's test with SES Group 5 (highest SES) as the control group and report the incidence rate ratios and their 95% confidence intervals.We used Wald R program.40 We used R packages, arsenal41 for summary statistics, spdep43 and raster44 for spatial analysis and overlays, glmmTMB45 for the GLMM, multcomp46 for the Dunnett test, and performance47 for checking multicollinearity. We extracted and plotted model estimates with the package sjPlot.48We performed all spatial and statistical analyses using the We provide summary statistics of census tract-level youth race/ethnicity and socioenvironmental attributes by the number of specialty vape shops in 2 concentrations were higher in census tracts with more vape shops, compared with census tracts without vape shops. In addition, the summary statistics of race/ethnicity and air quality data were similar between the final dataset used for statistical analysis and the larger vape shop counts at 71,927 census tracts (not shown).A higher proportion of SES Group 5 (highest SES) was found in census tracts with no vape shops than in census tracts with vape shops. Median NOI test statistic and density plot of permutation outcomes (not shown) indicated significant global spatial autocorrelation in specialty vape shop counts in census tracts across the United States . As per model selection results, we analyzed the statistical association of vape shop counts at census tracts with race/ethnicity, SES, and median NO2 variables using a negative binomial GLMM  and environmental hazard attributes nationally. We identify disparities in vape shop incidence at the census tract level based on strict criteria for inclusion of vape shops, thereby controlling for confounding effects of tobacco retailers selling different products.25 or operate at the school district level.21 Employing a robust SES measure that indicates social advantages/disadvantages is a strength of our study. Previous national and regional assessments examining vape shop density association with neighborhood SES used one or few specific indicator variables , with mixed results. For example, among national assessments, Dai et al.25 found no significant association of poverty and vape shops, while Venugopal et al.21 found a negative association.This approach differs from previous national assessments that either include retailers that also sell other tobacco productsFurthermore, due to our focus on cumulative risks experienced among youth, we examined race/ethnicity associations using census race/ethnicity data only for the population under the age of 18. At the census tract level, we found that the numbers of specialty vape shops decreased in relation to the proportion of youth represented by each of the race/ethnicity categories we examined. Particularly, we did not identify disparity in vape shop incidence in relation to youth race/ethnicity.25 The divergent results could be attributed to the higher racial/ethnic diversity among youth, with increased minority proportion, compared with the overall U.S. population.34This result contradicts findings of previous national assessments that used race/ethnicity data for the overall U.S. population; these studies found positive associations between vape shop density and the proportions of racial/ethnic minority populations.25 who reported a negative association of vape shop density with percentage of people under 18 years of age in urban areas.On the other hand, our findings are consistent with Dai et al.Broadly, our results help contextualize socioenvironmental determinants that may lead to tobacco-related health disparities in relation to e-cigarette products and the retail marketplace. The disproportionate occurrence of both specialty vape shops and traditional tobacco product retail outlets in low-SES neighborhoods raises public health concerns. Furthermore, the inequitable distribution of specialty vape shops in low-SES and poor air quality neighborhoods raises EJ and health equity concerns.28–30 The disproportionate distribution of specialty vape shops in low-SES neighborhoods may provide marginalized youth with greater access and exposure to e-cigarette products, marketing, and advertising, which may potentially result in greater use26 and disproportionate health impacts. In addition, chronic exposure to NO2 concentrations is associated with the development of asthma and increased susceptibility to respiratory infections, especially among youth.38Recent reports indicate that e-cigarette usage may be associated with higher likelihood of asthma and chronic obstructive pulmonary disease.2 concentrations than higher-income populations.10 The increased incidence of vape shops in poor air quality neighborhoods, particularly in an urban context25 with increased traffic emissions,37 further points to potentially disproportionate impacts on disadvantaged populations due to cumulative social and environmental risks.Particularly, lower-income populations in the United States are disproportionately exposed to outdoor, residential, average NOOur study results should be interpreted with several limitations in mind. We employed a cross-sectional design examining a highly dynamic retail sector using a dataset compiled before regulatory implementations, such as restrictions on certain flavored tobacco products, and the global COVID-19 pandemic. The race/ethnicity findings in our study are not reflective of multiracial youth who are not Hispanic or who belong to other racial/ethnic categories that we did not examine.We excluded vape shops that sell other tobacco products along with e-cigarettes to reduce their potentially confounding influence on associations at the census tract level. These retailers are still sources of exposure to tobacco product marketing and sale, and our findings may not reflect their influence. In addition, 1.40% of the total specialty vape shops were not included in the census tract data for final analysis due to differences in SES composite index data availability.We suspect this is a relatively minor factor that is unlikely to have affected results as the summary statistics of race/ethnicity and air quality data were similar between the reduced and the larger datasets. Finally, our study findings are limited in terms of drawing inferences about actual disparities in health outcomes; rather, our results are most useful for identifying socioenvironmental contexts and determinants that may potentially lead to tobacco-related health disparities.Nevertheless, we provide an overall robust EJ assessment characterizing U.S. specialty vape shops as cumulative environmental health risk factors for disadvantaged populations.26Our results—the inequitable occurrence of vape shops in low-SES neighborhoods—provide context for understanding potential disproportionate impacts on disadvantaged communities, especially youth, which may result from the increased presence of e-cigarette retailers in their neighborhoods. This may include increased exposure to e-cigarette labeling and advertising and increased opportunities to purchase e-cigarettes.50 Our results may also inform postmarket reporting requirements related to advertising and promotion of e-cigarette tobacco products in retail settings, similar to those described in the market orders for General Snus smokeless tobacco products.51This finding may provide useful background information for the U.S. Food and Drug Administration's review of applications to market e-cigarette tobacco products , particularly in terms of impacts on marginalized populations.26 Retailer-focused strategies aimed at limiting youth exposure to e-cigarette labeling and advertising; preventing sales to minors; and limiting retailers in low-SES neighborhoods may reduce susceptibility and initiation and help prevent tobacco-related health disparities due to youth e-cigarette use.26As disadvantaged communities are disproportionately exposed to e-cigarette retailers, our results add to growing evidence on the e-cigarette retail environment as an appropriate locus for policies to improve equity.Our results may inform policy efforts, such as local ordinances, which limit tobacco retail licenses based on overall density of tobacco outlets to prevent disproportionate impacts on socially disadvantaged communities. Our results may also help target efforts to prevent youth initiation and curb youth vaping  in socially disadvantaged neighborhoods.Overall, our study provides a baseline characterization of how specialty vape shops contribute to the cumulative social and environmental hazards to which socioeconomically disadvantaged youth are exposed. Study findings can provide useful contextual information for regulators and may inform future research and local policy efforts aimed at reducing tobacco-related health disparities and promoting equity.


The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus causing the coronavirus disease 2019 (COVID-19) pandemic is known to lead to the complicated sequelae of severe acute respiratory distress syndrome. Proning has been used as an adjunctive treatment to improve oxygenation in both ventilated and non-ventilated patients. Although patients respond well to this strategy, complications from this arise as well. It is hypothesized that COVID-19 intensive care unit (ICU) proned ventilation is associated with new cases of foot drops or compressive unilateral ankle dorsiflexion weakness during the early 2020 COVID-19 pandemic. Five patients presented to an acute rehabilitation facility with unilateral ankle dorsiflexion weakness after ICU proned ventilation during the COVID-19 pandemic. Three patients were found to have primarily subacute left sensory-motor dysmyelinating common peroneal neuropathies located around the fibular head. Two patients were found to have primarily subacute sensory-motor dysmyelinating right-sided common peroneal neuropathies above the fibular head and distal to biceps femoris muscle. Compressive unilateral common peroneal neuropathies during the pandemic are possibly related to the impromptu, unconventional, and unfamiliar use of proned ventilation. The coronavirus disease COVID-19) virus can cause a spectrum of sequelae, the most serious being fatal acute respiratory distress syndrome (ARDS) and multi-organ failure in patients worldwide. The prevalence of ARDS in COVID-19 patients during early 2020 was about 17% 9 virus c.Many hospitals have developed their own variation of the proning protocol. One of the commonly used proning methods is the “Cornish Pasty” technique . The “CoProning is maintained with body positions alternated on an average of every 2-4 hours for 16-18 hours prone in either the swimmer’s position or other positions where the limbs are adjusted to avoid common pressure points -11. GhelGiven the assumed need for long duration of this position to maximize benefits, the side effects of this maneuver may have been overlooked, resulting in complications such as brachial plexus injuries, ischemic optic neuropathy, decubitus ulcers, tube dislodgements, transient desaturations, and compressive neuropathies ,5,11-16.Compressive neuropathies associated with mechanical ventilation in prone positioning are rarely cited in the literature. Some risk factors for neuropathies include severe weight loss, diabetes mellitus, habitual leg crossing, compressive masses, and fibrous bands . ElectroAlthough patients with COVID-19-related ARDS respond well to proning, complications have been identified in the literature, and are not limited to dermatological, cardiopulmonary, and neuromusculoskeletal conditions . It is hCases were obtained from the inpatient rehabilitation facility and acute hospital electronic medical records. Cases included in the study had the following criteria: 1) a history of being COVID-19 positive, (2) a history of ICU proning, (3) unilateral ankle dorsiflexion weakness, (4) admission to an acute inpatient rehabilitation facility from March to June 2020, (5) recent discharge from an acute care hospital from March to June 2020, and (6) electromyography (EMG) and nerve conduction studies (NCS) conducted to elucidate the etiology of unilateral ankle dorsiflexion weakness. The exclusion criteria for the cases were no EMG/NCS conducted, premorbid unilateral/bilateral limb or ankle dorsiflexion weakness, prior neuropathy, severe weight loss, prior nutritional deficiencies, compressive masses, or cancer metastasis. Institutional Review Board approval was not necessary given the fact that all care was performed according to the standard medical practice and that these trends were noted retrospectively. Five patients were found to satisfy the above inclusion criteria. See Table  a historThree patients on EMG/NCS had primarily subacute left sensory-motor, primarily dysmyelinating common peroneal neuropathies. Two patients had right-sided primarily subacute sensory-motor dysmyelinating common peroneal neuropathies. Three of the left-sided injuries were localized at or above the common peroneal nerve with conduction blocks at the superficial peroneal nerve. Two patients were found to have primarily sensory-motor dysmyelinating right-sided common peroneal neuropathy above the fibular head and distal to biceps femoris muscle. One patient had sural nerve involvement. Needle examination revealed abnormal potentials at peroneal innervated muscles. None of the patients revealed lumbar radiculopathy or plexopathy. See Figure It is possible that all patients with unilateral ankle dorsiflexion weakness developed them during the early 2020 COVID-19 pandemic with proned ventilation. The overwhelming hospital surge created a widespread lack of healthcare providers to turn patients in a timely manner. This quick impromptu implementation of an uncommonly and unfamiliarly used proned protocol possibly resulted in pressure-related injuries. Healthcare providers’ fears of entering the room frequently to change positions due to severe lack of personal protective equipment and uncertainty of viral infectivity while in the room may have been other factors contributing to poor adherence to the proning protocol, and thus, prolonged compressive neuropathy. The EMG/NCS studies and the observation of clinical improvement of patients after conventional rehabilitation support the possibility that the etiology was unilateral compressive neuropathy of the common peroneal nerve.It is still suspected that laterality may be related to positioning, which brings to light that the “swimmer’s position” should be modified to prevent compression neuropathy. Other metabolic and medical factors are not entirely excluded. COVID-19 pathological side effects may play some unknown role in exacerbating conditions for unilateral ankle dorsiflexion weakness. Weight loss may have also played a role but occurs via a different pathological mechanism. Studies have shown that weight loss-associated foot drops are usually seen with habitual cross-legging, its predilection for both unilateral and bilateral nerve compression, and prior history of weight loss of greater than 25 pounds usually due to dieting, bariatric surgery, and anorexia .In conclusion, the cases presented here on the impromptu, unconventional, and unfamiliar use of proned ventilation during the early 2020 COVID-19 pandemic are possibly associated with new cases of compressive unilateral common peroneal neuropathy. In the future, larger-scale studies need to be conducted to validate this association. Improving the detection and reduction of compressive neuropathies may start with further investigation of the safety of the proning protocol. Rehabilitation from any illness is often a long process, and similarly, compressive neuropathies can be debilitating, and it may take up to a year to achieve maximal healing. While proning should continue to be utilized as dictated by the current literature, changing patient positioning at shorter intervals should continually be emphasized along with the early inclusion of physiatrists to better evaluate the need for timely mobilization. Individualized institutional guidelines should be developed and discussed with all involved.


Alu short interspersed elements (SINE) that have more than a million copies in primate genomes, are a significant source of homologous units and a verified target of gene conversion. The consequences of such a recombination-based process are diverse, including multiplications of functional TE internal binding domains and, for evolutionists, confusing divergent annotations of orthologous transposable elements in related species. We systematically extracted and compared 68,097 Alu insertions in various primates looking for potential events of TE gene conversion and discovered 98 clear cases of Alu–Alu gene conversion, including 64 cases for which the direction of conversion was identified . Gene conversion also does not necessarily affect the entire homologous sequence, and we detected 69 cases of partial gene conversion that resulted in virtual hybrids of two elements. Phylogenetic screening of gene-converted Alus revealed three clear hotspots of the process in the ancestors of Catarrhini, Hominoidea, and gibbons. In general, our systematic screening of orthologous primate loci for gene-converted TEs provides a new strategy and view of a post-integrative process that changes the identities of such elements.The process of non-allelic gene conversion acts on homologous sequences during recombination, replacing parts of one with the other to make them uniform. Such concerted evolution is best described as paralogous ribosomal RNA gene unification that serves to preserve the essential house-keeping functions of the converted genes. Transposed elements (TE), especially  Genomes of most eukaryotic organisms contain a large number of repetitive sequences, a notable portion of which is composed of transposable elements (TE). For example, TEs occupy up to 69% of human genomes . DespiteAlu SINE to an older element. Roy et al. [AluYa5 subfamily. A whole-genome gene conversion analysis among Alus in humans [Alu sequences revealed significant levels of gene conversion, especially among neighboring Alus. The authors found that gene conversion acts on Alus within a range of about 10 kb, inversely proportional to their distance from one another. Most studies of gene conversion between TEs focused on Alu SINEs in primates. However, similar effects were also reported for LTRs in other mammals [Due to their repetitive nature, high similarity, and large quantities in the genome, TEs present a significant substrate for non-allelic gene conversion. Gene conversion is a process whereby the genetic material of a donor sequence unidirectionally replaces that of a homologous acceptor sequence via recombination after a double-strand DNA break. Thus, gene conversion can proliferate mutations among TEs independently of the activity of the master-copy, leading to TE homogenization, a phenomenon known as concerted evolution . Earliery et al.  suggesten humans  focused  mammals ,10 and i mammals .Drosophila [As the vast majority of genomic TEs are neutral to the effects of natural selection, gene conversion does not usually have a crucial impact on the organism. However, TE gene conversion can have an adaptive effect in rewiring regulatory networks (reviewed in ). For exosophila .AluYh3a3 subfamily [Gene conversion may also directly influence the evolution of TEs ,14. Tranubfamily . Moreoveubfamily .Alu elements are the most abundant TEs in primate genomes and have served as a model group for TE-based gene conversion studies e.g., [Alus evolved from 7 SL RNA around 65 million years ago in the ancestral lineage of primates and consist of dimeric sequences of about 300 nt . They dic space . Becauseic space ), not on 3′-AluY ,22, FiguAlus are rare in primates, confirming their usefulness as virtually homoplasy-free markers in phylogenetic studies [Alu type with another in a monophyletic species group can lead to an incorrect conclusion about their phylogenomic relationship. Therefore, to determine the extent of possible homoplasy caused by gene conversion and the frequency of gene conversion in TEs of different ages, we performed a systematic screening for gene conversion among Alu elements belonging to clearly different primate Alu subfamilies and types (AluY/AluS and AluY/AluYc).Changing the TE type via gene conversion might impact the global genome architecture and, for genome scientists, may also lead to faulty genome annotations and obstruct TE-based phylogenetic reconstructions. The phylogenetic presence of identical orthologous TE elements in several species indicates their close relationships, the identification of which can be compromised if gene conversion results in altered element types. We previously showed that parallel insertions and precise deletions of  studies . HoweverAlu SINE gene conversion, we initially surveyed a published human genome RepeatMasker file to find all Alu SINE insertions. Because recurrent Alu clusters inhibit finding orthologous loci, we used fastCOEX to extract (nearly) complete human Alu elements with flanks largely free of additional TE sequences. The selected loci were then submitted to the 2-n-way computer suite to find all orthologous sequences of related primates. A subsequent RepeatMasker analysis of all individual hominoid TE regions revealed potential gene converted cases.To identify potential incidences of Alu element genomic coordinates from the human genome RepeatMasker outfile  from the Genome Browser, University of California Santa Cruz (UCSC) , accessed on 9 June 2021). Using the fastCOEX program  [Alu elements (≤20 nt 5′-/3′-truncations) located in regions largely free from additional repeats (≥70% of 700 nt flanks repeat-free). Due to the high divergence of older AluJ elements from their consensus sequences, we restricted our analyses to younger AluY/Yc and AluS elements.We extracted target ne 2021) , we seleAlu elements in primates we used the 2-n-way suite [AluS, AluY, and AluYc elements and orthologous regions in other hominoids. N-way generated presence/absence tables, indicating the presence or absence of Alus for all investigated primate species. We extracted sequences of loci in which (1) the targeted elements were present in all Hominoidea; (2) the targeted elements were present in all Hominidae except gibbon; and (3) the elements were present in human, chimpanzee, and gorilla but absent in orangutan and gibbon.To screen for orthologous ay suite . We firshttps://www.repeatmasker.org/RepeatMasker, accessed on 9 June 2021), we identified the family affiliations of AluS, AluY, and AluYc hg38 orthologs for all investigated non-human primate species. For orthologous primate loci in which different Alu element subfamilies/types were detected , we performed an extensive alignment analysis using the Phylogenetic Data Editor . To help reconstruct the evolution of gene-converted loci we supplemented the analyses with orthologous sequences of bonobo and a second gorilla individual (gorGor5). To identify the ancestral states of the Alu insertions, we also analyzed the sequences of at least one representative Old World (Macaca mulatta) and New World  monkey outgroup. The macaque and marmoset sequences were retrieved via genome blast for potentially gene converted loci and added to the alignments. All alignments were supplemented with respective Alu consensus sequences.Using a local version of the RepeatMasker , respectively. For AluY/Yc gene conversion, we considered all AluYs (without 12-nt diagnostic deletion at the 5′-end of the consensus) and all AluYs with the specific deletion , respectively. Furthermore, we accepted as gene converted only those loci with deviating Alu types from species that were phylogenetically nested within their related primates  or, alternatively, an AluS insertion in the ancestral lineage of Hominoidea with a subsequent precise deletion and precise insertion of AluY in the human lineage. Another conceivable scenario includes the specific accumulation of mutations in the diagnostic positions leading by chance to a change of Alu types. However, we accepted only cases in which at least three specific neighboring mutations were necessary to change the Alu subfamily or type. Thus, for all these cases, a single gene conversion event represents the most parsimonious explanation.We accepted specific  AluY/Yc . For Aluprimates . These dAlus in the human genome, we conducted additional analyses. Alu elements were extracted as described in Alu subfamily/type affiliations of 5′- and 3′-monomer pairs. If they were assigned to different subfamilies/types by at least three coherent diagnostic changes, we performed a manual analysis including other primate species (see To search for hybrid cies see  and recoWe supplemented the loci with gene conversion in the human lineage (after the human-chimpanzee split) with genomic information of additional human individuals. We retrieved 35 human genomes available in NCBI for which the ethnical origin was described.Alu element regions. To evaluate the “lowest verifiable level” of homoplasy caused by Alu–Alu gene conversion, we followed the calculation published in Doronina et al. for homoplasious deletions and insertions [Alus inserted before the Catarrhini diversification. Accordingly, we calculated the ratio of gene converted Alus in the human and chimpanzee lineages compared to the total number of Alu insertions in the common ancestor of Catarrhini.We applied two quality controls: (1) at least two sources of data  were used to verify gene conversion, (2) restricting comparisons to secured orthologs by omitting “low complexity” concatenated sertions . We applAlu–Alu element type change via gene conversions. Two recently developed tools were combined to find 98 specific cases of gene conversion. fastCOEX derived Alu loci with almost TE-free flanks, and 2-n-way extracted their orthologous sequences in various primate species. Gene conversion is identifiable when different Alu subfamilies or types recombine . From a RepeatMasker report of the human genome using fastCOEX [AluS and 12,689 AluY/Yc full-length elements with flanking regions largely free of other repetitive sequences. However, restricting our screening to these most reliable cases of Alu TEs reduces the total dataset of human Alus (~800.000 for AluS plus AluY) by about a tenth. We used the 2-n-way computer suite to retrieve 46,285 targeted AluS and 8099 AluY/Yc elements orthologous loci for a set of hominoid species . The other half was found in the intergenic areas of the genome  were replaced by younger, potentially active AluY elements (AluYs exhibited their main activity starting with the divergence of Catarrhini) [AluS and AluY elements, we detected gene conversion of the complete acceptor element, whereas in the remaining 38 loci only partial gene conversion occurred, leading to “mosaic” or hybrid elements . It should be mentioned that AluY/AluS gene conversion events resulted in hybrids of AluY 5′-monomer and AluS 3′-monomer (12 cases) can also be potentially AluSc8/AluS gene conversion because the 5′-monomer of AluSc8 shares the diagnostic mutations of AluY and the 3′-monomer of AluS. Furthermore, we detected an additional 31 cases of hybrid elements, in which we were unable to assign the pre-conversional state of the Alu elements  . This suarrhini) . Howeverelements , line 9.volution .AluY elements , whereas 31 gene conversions occurred on the terminal branches of other investigated primates . Within d3a1_gib ), which https://genome-euro.ucsc.edu/cgi-bin/hgGateway, accessed on 9 June 2021) and found 12 gene conversions , gene conversion was only detected in some human individuals. Contrary to our expectations, we could not find a phylogenetic pattern of the gene conversion distribution among 35 individuals. Orthologous Alu gene conversion was found in 2 of 9 African individuals, 5 of 13 Asian, 1 of 4 American, 1 of 1 Puerto Rican, and 5 of 8 European individuals. We suggest that such a mosaic of gene conversion events might result from duplication of Alu loci in the human genome with the subsequent gene conversion in one of the copies. Alternatively, multiple independent conversions could have occurred.We conducted a population analysis of human-specific gene conversions (6 cases), including 35 human individual genomes from Africa, Asia, America, and Europe . We founAlu subfamily or type affiliations in selected hominoids. It should be noted that because of sequence similarity, gene conversion occurs most frequently among identical or closely related elements, and is then unrecognizable. Here we showed that AluS/Y/Yc gene conversion occurred in all hominoid lineages. We suggest that the observed patterns of Alu–Alu gene conversion in hominoids are also representative of other primate species and TE types.In the present study, we examined gene conversion events leading to changes in the Alu elements in primates. However, they did not examine gene conversion. Although Aleshin et al. [Alu–Alu gene conversions, their screening method (ignoring diagnostic Alu positions) does not evaluate the contribution of gene conversion to homoplasy. Similar to the data in Doronina et al. [Alu insertions present in the Catarrhini ancestral lineage. Thus, we provide evidence for the existence of homoplasy caused by gene conversion, but show that the frequency is even lower than parallel insertions or precise deletions.Parallel insertion, exact deletion, or gene conversion might lead to apparently conflicting presence/absence patterns at orthologous loci. Doronina et al.  showed tn et al.  found a a et al. , we estiAlus via gene conversion was shown to be a frequent phenomenon [It should be mentioned that the classical, distance-based (the divergence of a TE sequence from a consensus sequence) calculations of the ages of TEs used in evolutionary studies might be distorted by gene conversion ,11,30. Oenomenon .Alu SINEs with different subfamily or type affiliations in primates). Many potential incidences of partial gene conversion were detected that resulted in hybrid elements. Incidences of gene conversion in TEs are frequent enough to visualize by genome-level screenings but rare enough that they do not challenge large-scale phylogenetic TE presence/absence studies.In summary, the footprints of gene conversion are directly detectable by genome-wide comparisons of deviating annotations of orthologous TEs in different species (e.g., orthologous


Anorexia nervosa (AN) is a persistent psychiatric disorder that is marked by abnormal reduced weight and amenorrhea, which may be primary or secondary. AN affects multiple endocrine axes such as gonadal, thyroid, and adrenal axis, growth hormone, and insulin-like growth factor-1, adipokines such as leptin, gut peptides like ghrelin, peptide YY, and amylin. As a result of these changes bone mineral density is reduced, which increases the risk of bone fracture in patients. In this review, we focus on substantial endocrine alterations in AN with a particular emphasis on the severe bone loss associated with this condition and current bone therapies. The disorder primarily affects girls and women, who are the focus of this review. Although the majority of AN-related endocrinopathies improve over time, long-term consequences such as short stature, osteoporosis, and infertility may occur. To avoid serious consequences, nutrition therapy in these patients requires a full understanding of bone complications, and new therapeutic options for treatment should be researched. Anorexia nervosa (AN) is a psychiatric condition characterized by an eating disorder with endocrine dysfunction. It mainly affects females during adolescence and its etiology is not yet clear or known. The prevalence of this condition among adolescents is around 1% with an annual incidence of new cases 10/100,000 between the ages of 15 and 19. The main characteristics of anorexia are underfeeding and fear of being overweight .Also, several hormonal changes occur including somatotropin resistance with low insulin-like growth factor-1 (IGF-1) levels, hypothalamic hypogonadism, relative hypercortisolemia, and changes in appetite-regulating hormones including leptin, ghrelin, and peptide YY (PYY). These contribute to abnormalities in bone metabolism resulting in low bone mass, impaired bone microarchitecture, and increased risk for fracture. They also negatively impact cognition, emotions, and mood. As AN affects women predominantly, amenorrhea is one of its serious complications . We havePhysiological estrogen replacement should be used to improve bone resorption rates and measures of trait anxiety in adolescents with AN. The best strategy is to boost all biological outcomes such as a menstrual recovery and an electrolyte repletion for profound malnutrition and dehydration for weight gain. Other medications examined to improve bone results include testosterone and IGF-1 replacement, dehydroepiandrosterone (DHEA) with oral estrogen-progesterone combination tablets, bisphosphonates and teriparatide .Although AN was first described centuries ago, the associated risk factors and etiology remain poorly understood and there is little data about it . This arHypothalamic-pituitary-gonadal axisThe most well-known endocrine complication of AN is amenorrhea which can be primary or secondary. Hypothalamic amenorrhea is believed to be caused by decreased energy availability in anorexic patients. In previous years, amenorrhea was a significant diagnostic criterion for AN, but because vulnerability to neuroendocrine dysregulation is exceedingly varied, the DSM-5 criteria no longer include amenorrhea as a crucial factor of the diagnosis acknowledging that many women with all the psychiatric features of anorexia and extremely low weight have regular menstrual cycles .In 1974 Boyar et al. published an article in which he described multiple dysregulated luteinizing hormone (LH) pulsatility patterns in amenorrheic women with AN. The patient's LH pulsatile secretion resembled prepubertal or early pubertal girls with either exceptionally low pulse amplitude or increased during sleep. Studies at that time focused on the role of leptin as a regulator of gonadotrophin-releasing hormone pulsatility, which was thought to be responsible for amenorrhea in women with AN .Some studies focused on kisspeptin  and its inactivating mutations that lead to pubertal failure. Kisspeptin has been observed to exhibit gonadotropin release in women with hypothalamic amenorrhea but there has been no research specifically examining its effect on AN .Although weight loss usually precedes amenorrhea, some patients experience amenorrhea before weight loss and others reach an extremely low weight while still having a reproductive function . This vaIn contrast, compared to a laboratory-generated normal range, DHEAS levels in adolescent girls were shown to be low. If any, the effect of a relative androgen deficiency in women with AN remains unknown. Nonetheless, they may result in muscle or bone mass loss and adverse mood effects .According to some studies, androgen levels have an inverse association with the degree of depression and anxiety symptoms in women with AN regardless of weight suggesting that relative androgen deficit may contribute to the severity of mood-related symptoms in these individuals. Low-dose testosterone in replacement dosages has been shown to have favorable mood effects in different adult female populations with few adverse effects. Thus, low-dose androgen treatment alone or in conjunction with other medicines may be a beneficial treatment strategy for managing mood comorbidities in women with AN but more research is needed .The growth hormone (GH) insulin-like growth factor-1 (IGF-1) axisIn AN, high GH and low IGF-I levels indicate a nutritionally mediated acquired resistance to GH. Low amounts of GH-binding protein have also been reported. Refeeding can help to reverse abnormalities in the GH-IGF-I axis ,15.According to a deconvolutional analysis of GH pulse investigations in adolescents and adults, raised basal secretory rates and higher frequency of secretory bursts underpin the GH excess in AN . These sHypothalamic abnormalities leading to excessive GH due to low somatostatinergic tone or high GH-releasing hormone have also been reported . Muscle Hypothalamic-pituitary-thyroid axisIn people with AN, hypothyroidism symptoms such as bradycardia, hypothermia, hypotension, dry skin, and a slowed metabolic rate are prevalent. Due to defective peripheral conversion, anorexic patients have a similar biochemical constellation of thyroid hormone abnormalities to a sick euthyroid syndrome with low triiodothyronine (T3) levels and low to normal thyroxine (T4) levels. Thyroid-stimulating hormone levels are usually normal to slightly below average in AN patients . These pThyroid hormone levels are altered for a variety of reasons in people with AN. In anorexia, like in any chronic disease or starvation, peripheral deiodination of T4 to T3 is reduced and conversion to inactive reverse T3 is enhanced . The hypAs previously stated, the biochemical thyroid abnormalities were seen in AN usually resolve with weight gain. But unfortunately, gaining weight by itself will not alleviate psychological issues or personality attributes. Thyroid disease is not the primary cause of psychological disorder although it can exacerbate pre-existing psychological difficulties .Hypothalamic-pituitary-adrenal axisIn AN, plasma cortisol levels rise regardless of whether urinary-free cortisol levels are elevated or normal . AccordiRecently Foppiani et al. demonstrated that desmopressin does not stimulate adrenocorticotropic hormone (ACTH) and cortisol in AN patients. This could be linked to the downregulation of hypophyseal 1-deamino-8D-arginine vasopressin (DDAVP) V3 receptors in AN . The dex Adipokines and appetite-regulating hormonesIn AN, adipokines like adiponectin and leptin (an anorexigenic hormone) are disrupted as are other appetite-regulating hormones including ghrelin (orexigenic) and PYY. Because of reduced basal leptin secretion and pulse amplitude, people with AN have low leptin levels. Adequate leptin concentrations allow the hypothalamic-pituitary-gonadal axis to function normally and reduced leptin levels in AN may lead to inadequate gonadotropin production . Women wGhrelin promotes the production of GH and ACTH while decreasing the production of LH and follicle-stimulating hormone. In adults and adolescents with AN, increased basal secretion and secretory pulse amplitude boost ghrelin levels. Higher ghrelin levels are a suitable adaptation to drive food intake during hunger, produce more elevated GH and cortisol release, and decrease gonadotropin secretion. Ghrelin may also have anabolic effects on the bones. Increased ghrelin levels predict higher BMD in healthy adolescents but not in AN suggesting ghrelin resistance in AN .Although some studies in adults find unchanged or reduced levels of PYY (an anorexigenic hormone), PYY levels are higher in adults and adolescents with AN compared to controls. Higher PYY levels are associated with lower fat mass. PYY can influence gonadotropin secretion and is detrimental to osteoblast function. Higher PYY levels are linked to lower bone turnover markers in adolescents with AN and lower BMD in adults .Central peptides changes in anorexia nervosaIt has been suggested but not definitively proven that peptide changes, even when caused by malnutrition or abnormal eating habits, may have a role in the origin and maintenance of some clinical elements of AN altering the course and prognosis. Tortorella et al. focused on the physiology of central and peripheral peptides that significantly impact eating behavior, body weight, and energy homeostasis in AN patients . In TablBone consequences in anorexia nervosaOsteopenia is a common and typically long-term complication of AN resulting in clinical fractures and an increased risk of fracture throughout life. A study of women with AN in their mid-twenties found that 55% of them had osteopenia and 35% had osteoporosis, with only 15% having a normal BMD at all skeletal locations studied. In people with AN, the annual rate of loss in BMD at the spine and hip is about 2.5% .A study by Vestergaard et al. described an increase in fracture risk. Reduced markers of bone production and higher markers of resorption have been observed in adults leading to the concept that osteopenia is caused by low osteoblast and high osteoclast activity. On the other hand, AN causes a generalized drop in bone turnover markers during adolescence, which is generally a time of substantial bone turnover .During adolescence, the impact of AN on bone is especially concerning. Adolescence is a period of increasing bone formation as a person approaches peak bone mass, which is a crucial indicator of future bone health and fracture risk. Bone accrual rates are substantially reduced in adolescents with AN resulting in a steady fall in bone density Z-scores . In addiAN affects both cortical and trabecular bone; however, trabecular bone is more severely impacted than cortical possibly reflecting the substantial impact of estrogen deprivation . Dual-enSOST gene and a glycoprotein released by osteocytes, has also been associated with the effects of estrogen on bone. Sclerostin reduces osteoblast activity by blocking Wnt signaling and increases osteoclasts by boosting RANKL activation of the receptor activator of nuclear factor k-B [Hypogonadism and later menarchal age are significant contributions to low BMD associated with AN. Estrogen reduces the activity of the receptor activator of nuclear factor k-B ligand (RANKL) and limits the release of proinflammatory cytokines through increasing osteoprotegerin (OPG). Proinflammatory cytokines are prevalent in AN, which may contribute to bone loss. OPG levels are high in AN and are inversely related to BMD despite low estrogen levels . Reducedctor k-B . Higher ctor k-B . Other hctor k-B .Current treatments for bone diseaseVarious therapeutic techniques have been investigated for the treatment of bone disease in AN with variable outcomes. In hypogonadal women, estrogen replacement with oral contraceptives makes intuitive sense but there is no proof that exogenous estrogen is genuinely effective.Although bisphosphonates improve bone density, maintaining a healthy body weight has a more significant long-term impact on bone density. The use of bisphosphonates in young women with AN presents obvious issues as these women may wish to become pregnant once they have recovered and the safety of these medications during pregnancy has yet to be proven. Studies of bisphosphonates have been observed to exhibit improper calcium homeostasis and fetal bone growth in pregnant rats .Menatetrenone (vitamin K2) has shown promise to reduce vertebral bone loss, boost bone formation markers, and decrease bone resorption signs in patients with AN . In thosBone development is promoted by recombinant IGF-1, which inhibits bone resorption. It improves bone health in people with GH insufficiency  . RecombiNutritional rehabilitation and behavioral support for bodyweight maintenance are essential and should be the cornerstones of AN treatment. Unfortunately, adolescent bone deficiency can lead to a lifelong loss in bone density even if weight is regained .LimitationsThere were several limiting factors while we searched for materials for this review. Our data came primarily from open-access articles written in English. Hence, some closed-access articles and articles published in other languages may have been missed.AN is a primary psychiatric disorder characterized by severe endocrine disorders and severe bone loss. Nutritional rehabilitation usually reverses abnormalities in the adrenal and thyroid glands; nevertheless, there may be long-term consequences such as short stature, infertility, and osteoporosis. Some problems persist after recovery and may contribute to illness progression and relapse. Currently, there are no FDA-approved medications for low BMD treatment in anorexia nervosa; therefore, weight gain and menstruation recovery remain the most effective strategy to increase BMD. In adolescent AN, physiologic estrogen replacement  improves BMD and studies are ongoing to assess the influence of IGF-1 replacement on bone density and structure. Further research is essential to better understand the disease's etiology and complications and to find effective treatments for AN and its comorbidities.


In seventy years, solid organ transplantation (SOTx) has progressed from a high-risk experimental procedure, with few recipients surviving into the 2nd year post-transplant, to becoming the standard of care for many end-stage organ diseases –3. DurinDwyer and Turnquist). Here, we also made the case that poor outcomes after SOTx may result not only from abundant DAMP-driven inflammation supporting rejection, but also from inadequate or dysregulated DAMP-mediated tissue repair (Dwyer and Turnquist). Similarly, Ordikhani et al. make a convincing argument that macrophages have a dual role in allograft transplantation and can both trigger inflammatory responses or induce tolerogenic environments. They highlight the role of monocytes and macrophages in SOTx, summarize macrophage heterogeneity, and describe the role of macrophages in rejection versus tolerance. In particular, they highlight monocyte “trained immunity” that is associated with augmented immune responses and retained by epigenetic and metabolic changes. They further suggest that therapeutic targeting of trained immunity represents a novel paradigm to prevent allograft rejection. A review by Zhao et al. furthers similar considerations, first by making a strong case for innate immune cell involvement in allograft rejection, followed by a detailed review of how donor polymorphisms in SIRPα promote allorecognition by CD47 signaling on monocytes. This cascade causes accumulation of monocyte-derived DCs and initiation/maintenance of T cell responses. The authors then describe an innate memory response to MHC class I that is driven by paired immunoglobulin-like receptor A (PIR-A) molecules sensing allogeneic MHCI and contributing to SOTx chronic rejection. The authors close their review by contextualizing the impact of innate allorecognition and innate memory in relevant clinical scenarios.Articles in this Research Topic encompass Original Research and Reviews from transplant researchers seeking to understand the mechanisms controlling transplant outcomes beyond T cell recognition of donor MHC. It is widely accepted that allograft rejection results from coordinated interactions between the innate and the adaptive immune systems, where activated myeloid antigen presenting cells (APCs), such as dendritic cells (DC) or macrophages, stimulate alloreactive T cell responses. A number of the articles received focused on how innate immune cell can also act as direct effectors of transplant outcomes. In one review, we focused on the consolidating knowledge that damage associated molecular patterns (DAMPs) coordinate the function of innate immune cells to shape alloimmunity and rejection, but also direct graft tissue repair , a Sphingosine 1-phosphate receptor (S1PR) agonist, could protect against kidney ischemia reperfusion injury (IRI). Adoptive transfer of FTY-DCs significantly protected kidneys from IRI, a result dependent upon a recipient spleen, DC expression of S1P1, and functional viability of DC-associated mitochondria. Their report further implicates a mechanism involving transfer of mitochondria to splenic macrophages as an underlying mechanism and support this supposition by demonstrating the transfer of mitochondria from bone marrow-derived DCs to cultured macrophages. Molina et al. investigate DC biology in the context of GVHD by demonstrating that pre-transplant conditioning with bendamustine plus total body irradiation increased CD8α cDC1 cell number and percentage, a subset known to ameliorate GVHD  summarizes the current understanding of the metabolic pathways available to alloreactive T cells and highlights key metabolic proteins and pathways linking T cell metabolism to effector function. A current picture of alloreactive T cell metabolism during AlloHSCT is provided, with roles for glycolysis, fat oxidation, and glutamine metabolism as well as a potential explanation for how presumably contradictory metabolic findings might be reconciled. Finally, the caveats and challenges of assigning causality using the current metabolic toolbox, as well as future directions in the field, are summarized.Metabolic reprogramming is critical to T cell activation, differentiation, and function . Cheng eKim and Reddy describes current approaches targeting Signal 3 in clinical GVHD and reviews extracellular cytokine blockade, therapies that target intracellular cytokine synthesis, and pathways which impact cytokine transport, the latter of which represents a novel starting point for rational design of GVHD therapies (Kim and Reddy). In their work, Mammadli et al. demonstrate that as well as the intracellular signaling protein Interleukin-2-inducible T cell Kinase (ITK) is necessary in T cells for the development of GVHD but dispensable for graft-versus-leukemia (GVL) effects. Mechanistically, investigators noted a cell intrinsic decrease in proinflammatory cytokine expression and cell extrinsic decrease in CD8 T cell proliferation, as well as impaired chemokine expression in ITK knock-out cells, resulting in decreased migration to target organs. In their review, Gill and Burrack describe two concepts that expand the commonly held view of how memory cells contribute to transplantation immunity and tolerance disruption. First, they stress that autoimmune T cells may interact with graft-derived autoantigens in addition to cross-reactive, heterologous alloimmune MHC molecules. Additionally, they posit that a common APC may license naïve alloreactive T cells if a vaccine- or pathogen-directed memory cells recognizes the same APC in vivo. Indeed, this speculation is reminiscent of CD4 helper T cells licensing CD8 cytotoxicity and suggest that assessing only anti-donor MHC reactivity pre-transplant may insufficiently predict success in tolerance-promoting therapies. Understanding transplantation tolerance also requires knowledge of the crosstalk between pathogenic T cells and their tissue resident counterparts. In their review, Lei et al. focus on interactions between alloreactive T cell and cells of the liver microenvironment, paying particular attention to adhesion molecule, chemokine expression, cytokine secretion by immune cells, and a role for regulatory T cells in promotion of transplant-specific tolerance. The authors close with a review of recent and ongoing clinical trials that seek to influence post-transplant tolerance using cell mediated approaches.Other papers in the Research Topic provide novel insights into mechanisms shaping T cell functions after transplantation. Activation of GVHD-causing alloreactive T cells relies on TCR engagement  and coordinated co-stimulation , in concert with signals from a network of secreted cytokines . The review by The studies presented in this Research Topic show how our knowledge of transplant biology continues to not only increase, but also broaden into new roles for long studied immune cells and immunological mechanisms. There is clearly a rapidly advancing understanding of innate immunity, improved manipulation of immune cell metabolism, and functional elucidation of the pathways controlling pathogenic alloreactive immune responses cells in SOTx and AlloHCT. There has been a sustained history of observation, collaboration, and knowledge assimilation between research discoveries and clinician scientists in the fields of SOTx and AlloHCT. It is encouraging to see investigators in both areas in this Research Topic, and we hope that efforts like this help the diverse groups of transplant scientists learn from each other as we aim to provide transplant recipients with the best hope for long-term resolution with the least amount of toxicity.Both authors generated and edited the editorial. All authors contributed to the article and approved the submitted version.The authors are supported by NIH grants: R01AR073527 (HT), R01HL22489 (HT), R56AI139327 (HT), and R01HL144556 (CB), DoD grant CA180681 (CB) and a Hope on Wheels Scholar grant from the Hyundai Motor Company (CB).The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interestAll claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


Emerging evidence suggest that COVID-19 is associated with hypercoagulability, predisposing patients to increase risk of thromboembolism. Anticoagulation is not without its risks of bleeding and decision to initiate anticoagulation should be carefully considered with close monitoring. Spontaneous retroperitoneal hematoma is a rare complication, and there are only a few documented reports implicating anticoagulant or antiplatelet agents as a potential cause. We report a 57-year-old gentleman with COVID-19 pneumonia who developed hypotension on Day 10 of illness while on prophylactic anticoagulation. Computed tomography scan of abdomen revealed a large right retroperitoneal and psoas muscle hematoma and he underwent surgical exploration to evacuate the hematoma. His condition improved and was discharged well. Although prophylactic anticoagulation may reduce thrombotic complications in severely ill COVID-19 patients, a high index of suspicion for rare bleeding complications should be maintained if patients become hemodynamically unstable. Early diagnosis and appropriate intervention may improve outcome and prevent mortality. COVID-19, caused by SARS-CoV-2 virus, has caused a global pandemic since late 2019. Since its outbreak, COVID-19 has shown many different clinical manifestations. Although thrombosis is one of the hallmarks of this disease, the real incidence of bleeding in COVID-19 remains unknown due to lack of data reported in the literature. Thromboembolic events have been shown to be as high as 21% with a mortality rate of ~74% in COVID-19 infected individuals [We present an interesting case of large retroperitoneal and psoas hematoma while on prophylactic anticoagulation for severe COVID-19 infection.A 57-year-old gentleman with no known medical illness presented with history of fever, abdominal pain, diarrhea and non-productive cough for one week. Vital signs on admission revealed blood pressure of 147/83 mmHg, pulse rate of 81 beats per minute, temperature of 36.3°C and oxygen saturation of 96% under room air. His physical examination revealed that he is tachypnoeic with a respiratory rate of 26 breaths per minute with minimal coarse crackles over the right lower zone of the lung. Laboratory investigations showed that he has mild acute kidney injury on presentation associated with lymphopenia and elevated inflammatory markers . His iniPatient initially showed signs of improvement as he has improving cough and exertional dyspnoea with reduction in his C-reactive protein (CRP) levels. However, decision was made to continue him on prophylactic dose of enoxaparin as he was still dependent on nasal cannula for oxygen supplementation and his serial chest X-rays did not show remarkable improvement. Moreover, he was not ambulating well during his stay in ward. On Day 10 of illness, he developed hemodynamic instability with a sharp decrease in hemoglobin concentration from 12.9 to 5.2 g/dl. On clinical examination, he was tachypnoeic and pale with poor peripheral perfusion. Otherwise, other physical examination was unremarkable. There was no evidence of upper and lower gastrointestinal tract bleeding. Other laboratory investigations showed normal platelet count with severe lactic acidosis . He was intubated for respiratory distress and commenced on blood transfusion. A contrast-enhanced computed tomography (CT) scan of his abdomen revealed a large right retroperitoneal and right psoas muscle hematoma  and 2 meet al. [The risk of developing thrombosis in COVID-19 has been postulated to be triggered by the attachment of SARS-CoV-2 virus to the angiotensin-2 receptor of the endothelial cells, leading to release of proinflammatory cytokines, endothelial dysfunction and systemic inflammation. Although administration of anticoagulation may prove beneficial in COVID-19 infection, it has been associated with bleeding events. A study by Al-Samkari et al.  has showRecently, there are several papers reporting similar presentation of retroperitoneal hemorrhage as a complication of COVID-19. We identified five published case reports describing eight cases of bleeding events in COVID-19 . IncludiThe diagnosis of retroperitoneal hematoma requires a high degree of clinical suspicion as patients do not exhibit any clinically apparent signs and symptoms until a substantial amount of blood loss has occurred. It should be suspected in patients who present with significant groin, flank, abdominal, back pain or hemodynamic instability after an interventional procedure or in patients who are anticoagulated. A contrast-enhanced CT scan of the abdomen remains the imaging modality of choice in the diagnosis of retroperitoneal hemorrhage as it serves to identify the anatomical extension, size of hematoma and compressive complications or extravasation. The mainstay management of retroperitoneal hematoma consists of cessation or modification of anticoagulation therapy and volume resuscitation with fluid and blood products. Small hematomas with mild symptoms without displacement of retroperitoneal structures and without need for multiple blood transfusions may be treated conservatively. Other treatment options such as selective arterial embolization via interventional radiology or surgical exploration with evacuation of hematoma are reserved for patients with significant abdominal hypertension symptoms and who are hemodynamically unstable .There is no clear consensus regarding the management of retroperitoneal hematoma. Early detection and prompt intervention would result in a better outcome. We postulate that early intervention will reduce the expansion of hematoma and shorten the duration of compression of the surrounding tissues. There are controversies regarding prophylactic anticoagulation in patients with COVID-19 pneumonia. However, British Thoracic Society and Scottish Intercollegiate Guidelines Network suggest the use of prophylactic dose low molecular-weight heparin (LMWH) for patients who require admission and intermediate-dose LMWH (twice daily standard prophylactic dose) for patients on critical care . BesidesOur case report suggests that COVID-19 patients treated with anticoagulants are at risk of developing spontaneous retroperitoneal hematoma. Although rare, it should remain as a possible source of bleeding, especially when patients present with flank pain, anemia and signs of hypovolemia. Close monitoring and early intervention may improve the outcome in this group of patients.