Cytogenetic analysis of ۱۲۸۴ cases of Down syndrome

Among ۱۷۷۸۶ karyotyres performed in our center,during ۱۸ years (۱۳۵۷-۱۳۷۵),۱۳۰۰(۷.۳%) cases of chromosome ۲۱ aberration,including ۱۲۸۴(۹۸.۷۷%) of Down syndrome have been detected.۱۱۹۱ of cases (۹۲.۷۶%) born free trisomy ۲۱:۶۱ cases (۴.۷۵%) revealed translocation and ۳۲ cases (۲.۴%) showed mosaic pattern.among the pateints,۵۹ had robertsonian translocation,۲ had translocation between chromosome ۲۱ and a non acrocentric chromosome designated as chromosomes ۷ and ۸.among the ۱۲۸۴ patients with chromosome ۲۱ aberration,۷۳۵ were male and ۵۴۹ female with a Mto F ratio of ۱.۳۴:۱-cytogenetic study of ۱۸ parents of DS children with robertsonian translocation revealed that ۴ cases(۲۲.۲۲%) were inherited from the carrier mothers.there were also ۴ translocation in non G chromosomes,which were inherited from either parent.in general ۸ of the ۲۳ parents(۳۴.۷۸%) including ۶ mothers and ۲ fathers transmitted the involved chromosome to their children in the other ۱۵ cases primary translocation occured.two of the DS were also associated with klinfelter syndrome (۴۸,XXY+۲۱) and one male child born ۴۷,XY+۲۱, ۵p+Cri du chat).our findings are almost similar to the large group studies of other investigators.

Keywords:

trisomy of ۲۱ , down syndrome , cytogenetic , chromosomal translocation , mosaicism