A Japanese familial case of hypochondroplasia with a novel mutation in FGFR3

[Introduction] Gain-of-function mutations in the fibroblast growth factor receptor 3 gene (FGFR3) result in a group of skeletal dysplasias, such as prototypic achondroplasia (ACH: OMIM#100800) and lethal thanatophoric dysplasia (TD1: OMIM#187600). Hypochondroplasia (HCH: OMIM#146000) is the mildest of the FGFR3-associated skeletal dysplasias and is characterized by short stature with macrocephaly, brachydactyly, limited range of motion at the elbows, lumbar lordosis, and bowed legs. Radiological features of HCH are flared metaphyses, narrowed interpedicular distance, square ilia, and short femoral necks. These clinical and radiological signs are generally less pronounced than those seen with ACH and may not be noticeable until early or middle childhood. Because GH replacement is effective in some HCH patients (1, 2), genetic analysis to assist early diagnosis and intervention may improve the prognosis of these patients. Here, we present such an example and report the identification of a novel mutation in FGFR3 in a familial case of HCH and the effectiveness of GH treatment in the elder sister.