Split Hand/Foot Malformation (SHFM)

Abstract

Split-hand/foot malformation (SHFM) typically affects the central rays of the hands/feet, resulting in an extremely variable phenotype consisting of missing digits; aplasia and/or hypoplasia of the phalanges, metacarpals, and metatarsals; and syndactyly of the remaining digits. Two major anatomic types have been discerned. In the first, the hand is split into two by a cone-shaped cleft tapering proximally consisting of fused remnants of radial and ulnar ray fingers. Similar deformities can occur in the feet. In the even more severe type, only a single digit remains (monodactyly). As a general rule, the radial rays are usually absent, with only the 5th digit remaining. Besides these typical findings, a vast variety of less severe phenotypes can be observed that sometimes need close inspection, including radiographs, to not be overlooked. Other less frequent findings include preaxial involvement consisting of absent, proximally placed, and/or triphalangeal thumbs, as well as preaxial polydactyly. Nonpenetrance is another characteristic of SHFM. Many pedigrees have been described that indicate skipping of generations and extreme variability of phenotypes.