Acanthosis nigricans in a child with mild osteochondrodysplasia and K650Q mutation in the FGFR3 gene

A girl with a mild sporadic osteochondrodysplasia (OCD) similar to hypochondroplasia but with significant short stature is reported. She has been followed clinically between the ages of 9 months and 14 years. Growth remained normal throughout childhood with stature evolving about 3.5 SDs under the mean for age. By 8 years of age gradually appearing acanthosis nigricans (AN) in the neck and flanks was histopathologically confirmed. It provided the new incentive to search for specific FGFR3 mutations associated with this dermatologic abnormality. This resulted in the identification of the 1948A > C transversion predicting the K650Q missense substitution in the FGFR3 protein. Besides the expansion of the phenotypic spectrum of FGFR3-related OCDs to HCH with AN, this observation underscores the continuing adverse effect of this specific mutation upon the normal inhibitory signaling of the receptor at least in epidermal cells.