Trisomy/tetrasomy 21 mosaicism in CVS: interpretation of cytogenetic discrepancies between placental and fetal chromosome complements

    loading  Checking for direct PDF access through Ovid


Trisomy/tetrasomy 21 mosaicism was found in chorionic villi (semidirect preparation) obtained from a 40 year old pregnant woman.Since both cell lines were abnormal, the couple elected for pregnancy termination. Placenta and fetal tissue samples were obtained for cytogenetic study. Long term cultured villi showed a non-mosaic trisomy 21 karyotype, while other tissues showed either a normal karyotype or normal/trisomy 21 mosaicism. These discrepancies could be explained by a modified "bottle neck" embryogenic model with a trisomic zygote and a non-disjunction event taking place in one of the first divisions. Our case emphasises the need for confirmatory studies in other tissues when mosaicism is encountered in chorionic villi, even if all cell lines are abnormal.

(J Med Genet 1999;36:333-334)

Related Topics

    loading  Loading Related Articles