Achondroplasia and enchondromatosis: report of three boys.

We report on three boys suffering from achondroplasia concurrent with enchondromatosis-like metaphyseal changes. Two boys who were examined by molecular analysis harbored a mutation of FGFR3, which occurs in most achondroplastic individuals. Given the prevalence of achondroplasia and enchondromatosis, the metaphyseal changes in these patients are less likely to represent the coincidence of both disorders, but rather to result from a rare consequence of the FGFR3 mutation. Impaired FGFs/FGFR3 signaling pathway in achondroplasia inhibits chondrocytic proliferation, which accounts for most characteristics of achondroplasia. On the other hand, it causes conflicting biological consequences that can suppress or stimulate chondrocytic maturation. In a small subset of achondroplastic individuals, the suppression of chondrocytic maturation may outweigh the stimulation, which leads to cartilaginous overgrowth into the metaphysis, eventually causing the metaphyseal dysplasia found in the present patients.