Lys650Met substitution in the tyrosine kinase domain of the fibroblast growth factor receptor gene causes thanatophoric dysplasia Type I. Mutations in brief no. 199. Online

Thanatophoric dysplasia (TD) is one of the most common neonatal lethal skeletal dysplasias with micromelic shortening of the limbs, relative macrocephaly, flat vertebral bodies and a narrow thorax. TD has been divided into two types, type I (TD1) and II (TD2), based on clinical, radiological, histological, and molecular criteria. We identified a A to T heterozygous base subsitution at position 1949 predicted to cause a Lys650Met substitution in a term infant with TD1. This mutation has been previously described in one case of TD1 and three cases of severe achondroplasia with acanthosis nigricans and mental retardation. Interestingly, all cases with the Lys650Met mutation have the same unusual curvature of the tibia and/or fibula.