Congenital metacarpal fusion associated with polydactyly.

A case of congenital fusion of metacarpal bones with polydactyly is reported. The fusion occurred between the proximal parts of the third and the fourth metacarpal bones. The same type of anomaly was induced in rat fetuses by oral administration of myleran. The anomalies for which the critical period is the same as both metacarpal fusion and polydactyly, were analysed. From the results of the experimental study, the authors propose that the cause of the metacarpal fusion associated with polydactyly is the combination of a disorder of ectoderm-mesoderm interaction and a deficit of mesenchymal cells in the limb bud.