Prenatal diagnosis and molecular analysis of type 1 thanatophoric dysplasia

Abstract

Thanatophoric dysplasia (TD) is one of the most common lethal skeletal dysplasias with an estimated frequency of nearly 1 in 20000 births. It is characterized by extreme rhizomelia i.e. a normal trunk length but a narrow chest and a large head with a prominent forehead. The abnormality is classified into TD type 1 (TD 1) where patients always have curved femurs and sometimes a cloverleaf skull and TD type 2 (TD 2) where patients always have straight femurs and always a cloverleaf skull. The prenatal diagnosis of TD can be established by ultrasonography in the second trimester of gestation. However it is not always possible to differentiate TD from others skeletal dysplasias by ultrasonography alone and molecular genetic analysis of the fibroblast growth factor receptor 3 (fgfr3) gene is useful for prenatal diagnosis of TD. In this report 3 fetuses with TD 1 were diagnosed ultrasonographically in the second trimester and molecular analyses of the fgfr3 gene confirmed the prenatal diagnoses. (excerpt)