Developmental biology and classification of congenital anomalies of the hand and upper extremity.

Recent investigations into the mechanism of limb development have clarified the roles of several molecules, their pathways, and interactions. Characterization of the molecular pathways that orchestrate limb development has provided insight into the etiology of many limb malformations. In this review, we describe how the insights from developmental biology are related to clinically relevant anomalies and the current classification schemes used to define, categorize, and communicate patterns of upper limb malformations. We advocate an updated classification scheme for upper limb anomalies that incorporates our current molecular perspective of limb development and the pathogenetic basis for malformations using dysmorphology terminology. We anticipate that this scheme will improve the utility of a classification as a basis for diagnosis, treatment, and research.