Prenatal diagnosis of thanatophoric dysplasia in the second trimester: ultrasonography and other diagnostic modalities.

Thanatophoric dysplasia is the most common type of neonatal lethal osteochondrodysplasias, with an estimated frequency of nearly of 1 in 20,000 births. It is a disorder characterized by extremely short ribs, tubular bones and macrocephaly. The prenatal diagnosis of thanatophoric dysplasia has been well established by ultrasonography in the second trimester; however it is not always possible to differentiate the thanatophoric dysplasia fetuses from the others with skeletal dysplasias like fibrochondrogenesis or atelosteogenesis by ultrasonography. Recently, mutations in the fibroblast growth factor receptor 3 gene, located on the short arm of chromosome 4 have been identified as a cause of thanatophoric dysplasia. In this article we described the prenatal diagnosis of two fetuses with thanatophoric dysplasia at 18 and 24 weeks of gestation by ultrasonography. Postpartum radiological and histological analysis confirmed our prenatal diagnosis. Our purpose was to remind the differential prenatal diagnosis with other skeletal dysplasias and new prenatal diagnostic modalities.