XXXX : genetics, prenatal diagnosis, and future prospects.

@entity1 @entity4094 @entity3986 @entity1555 @entity4714
@entity1555 and @entity1555 are now understood at the genetic, biochemical, and molecular levels. At the genetic level, both disorders result from mutations of the X-linked gene encoding @entity4714 . At the biochemical level, @entity1555 results from the deficiency of a large protein called @entity4714 , whereas @entity1555 results when @entity4714 is present, though abnormal in either amount or molecular structure. To date, thousands of @entity1 have been analyzed for mutations of the @entity4714 gene in peripheral blood DNA or alterations of the @entity4714 protein in muscle tissue. The severity of the clinical phenotype of these @entity1 has been compared with their @entity4714 gene mutations and corresponding @entity4714 protein alterations, revealing an unexpectedly high degree of correlation. Thus, information derived from the molecular analysis (DNA or protein) of a particular @entity1 provides a "molecular diagnosis," which is highly predictive of the clinical course that @entity1 can be expected to follow. Because molecular diagnoses are independent of the @entity1 's age, they provide a prognosis for the large majority of @entity3986 @entity1 even before clinical symptoms of their disease become apparent. Such prognostic molecular diagnoses have proven particularly valuable when the @entity1 is an isolated case, with no family history for the disorder. Prenatal genetic diagnosis of @entity1555 or @entity1555 may involve use of Southern blot or PCR techniques to search for a deletion in the DNA of at-risk fetuses or more complicated family linkage studies using intragenic and flanking RFLPs. More recently, assay of @entity4714 content in fetal skeletal or cardiac muscle from at-risk abortuses has been accomplished, allowing definitive discrimination of affected and normal fetuses in cases in which deletion analyses and family DNA studies were equivocal. In utero fetal skeletal muscle biopsy for @entity4714 protein assay has actually been accomplished in at least one at-risk pregnancy in which family DNA studies were uninformative. @entity4714 was present in skeletal muscle from this 20-week-old male fetus, and the pregnancy continued, resulting in the term birth of a healthy male @entity1 . The future holds exciting opportunities for neonatal screening and treatment of these devastating @entity4094 .
