DOUBLE AUTOSOMAL GONOSOMAL MOSAIC ANEUPLOIDY - STUDY OF NONDISJUNCTION IN 2 CASES WITH TRISOMY OF CHROMOSOME-8/

We report cytogenetic and molecular investigations performed in two ca ses of mosaic trisomy 8 combined with mosaic sex chromosome aneuploidy . In a 35-year-old female, presenting with short stature, gonadal dysg enesis, and a multiple congenital anomalies/mental retardation syndrom e typical of trisomy 8, chromosome analysis from peripheral lymphocyte s showed the presence of three cell lines, whose karyotypes were 45,X (59.2%), 46,X,+8 (1.2%), and 47,XX,+8 (39.6%), respectively. The same cell lines were found in a skin fibroblast culture, though in differen t proportions. The second patient, a 9-month-old male with multiple sk eletal abnormalities, showed a 47,XY,+8 and a 47,XXY cell line in both peripheral lymphocytes (61.7% and 38.3%, respectively) and skin fibro blasts (92.8% and 7.2%, respectively). To determine the events underly ing the origin of these complex karyotypes we performed Southern blot and polymerase chain reaction (PCR) analysis using polymorphic DNA mar kers from the X chromosome and from chromosome 8. Both supernumerary c hromosomes 8, and, in case 2, the two X chromosomes, appeared to be id entical, lacking detectable recombination events. We conclude that, in both cases, the most likely mechanism underlying the origin of the mo saic cell lines was formation of a normal zygote, followed by mitotic errors during early divisions.