Pseudo dicentric chromosome (5;21): a rare example of maternal germline mosaicism

Karyotyping of a malformed male newborn revealed the unbalanced karyotype o f 46,XY, psudic(5;21)(q12;p13), +5 resulting in trisomy for the short arm o f chromosome 5 and partial trisomy for 5q. Both parents had normal karyotyp es in their peripheral blood lymphocytes. A second pregnancy ended in a mis carriage at 16 weeks gestation, sonographically 12 weeks. Karyotyping of ch orionic villi from the abortus revealed the same unbalanced karyotype that had been identified in the first child. Fluorescence in-situ hybridization analysis confirmed a trisomy 5p. Microsatellite marker analysis ruled out i llegitimacy and proved the maternal origin of the trisomic section of chrom osome 5. Extended chromosome analysis of 60 metaphase cells from maternal s kin fibroblasts and 40 metaphase cells from lymphocytes did not reveal mosa icism for psudic(5;21). These findings suggest the presence of a maternal g ermline mosaicism.