Prenatal diagnosis of the fragile‐X in male monozygotic twins: Discordant expression of the fragile site in amniocytes

Abstract
A prenatal diagnosis of the fragile‐X syndrome in monozygotic male twins is reported. The expression of the fragile site was discordant in amniotic cells. Fetal blood and, after therapeutic abortion, skin fibroblasts were positive in both fetuses. Our data suggest that great care should be taken when using amniocytes for prenatal diagnosis of the fragile‐X syndrome.