Fragile X Mutations Might Predispose to Turner Syndrome

Fragile X mutation (CGG triplet repeat expansion at Xq27.3) is the most common inherited form of mental retardation. The full mutation (i.e., expansion to >200 repeats) most often involves the maternally inherited X chromosome and leads to the fragile X mental retardation syndrome in males and some females. In a study of 423 DNA samples from female fetuses at risk for inheriting the fragile X mutation, investigators identified 106 fetuses with the full mutation. Five of the 106 female fetuses with the full mutation also had mosaic Turner syndrome, but none of the at-risk female fetuses without the full mutation had Turner syndrome. Isolated cases of mosaic Turner syndrome have been reported in females with the full-mutation, but this study …