Supernumerary XXXX ( @entity2100 ) and uniparental disomy 22 in a @entity1 with confined placental mosaicism of trisomy 22: trisomy rescue due to marker chromosome formation.

@entity1 @entity2100 @entity8882 @entity299
Trisomy rescue is one of various proposed mechanisms in formation of supernumerary @entity2100 ( @entity2100 ) and @entity8882 ( @entity8882 ). In the present report a small de novo marker chromosome derived from chromosome 14 or 22 was diagnosed at prenatal diagnosis due to maternal age. Follow up investigations at birth revealed mosaicism 47,XX,+mar/46,XX. Using FISH, the marker was positive for the probe D14/22Z1, but negative for the probes midi 54 and D22Z4. Using three informative markers both chromosomes 22 were shown to be inherited from the mother (UPDmat). The results are consistent with nondisjunction at maternal meiosis I. The @entity1 is 18 months old now and phenotypically normal. @entity299 were excluded by sonographic examinations. Motor and mental development is according to or ahead of developmental milestones (free walking with 10 months, first words at 12 months). The case confirms that maternal @entity8882 22 most likely is not associated with clinical abnormalities. According to FISH results, @entity8882 22, and 47,XX,+22 in the placenta, we conclude that the @entity2100 was derived from alpha satellite sequences of chromosome 22. This case for the first time gives evidence that early postzygotic reduction of a chromosome to a @entity2100 is a real existing mechanism to rescue a conceptus with trisomy.
