[Case of a Japanese female presenting severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN) syndrome with a K650M mutation in the fibroblast growth factor receptor 3 gene].

We diagnosed a Japanese female as having severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN) syndrome. Genetic analysis revealed a K650M point mutation in the fibroblast growth factor receptor 3 (FGFR3) gene, described in only six other individuals in the world. The medical history of the present case includes severe skeletal dysplasia at birth, progressive acanthosis nigricans in infancy, and severe central nervous system structural abnormalities, consisting of the absence of right cerebral hemisphere (hydranencephaly), ventricular dilatation, both indicating congenital brain malformation, and porencephaly indicating destructive brain damages. The patient is severely retarded and has suffered from intractable seizures. This is the first report of a Japanese patient and the seventh case of SADDAN syndrome confirmed genetically.