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Split hand-split foot (split hand-foot malformation, SHFM) is a rare malformation involving the central rays of the hands and feet, affecting randomly one to all four limbs. Syndactyly with oligodactyly, median clefts of the hands and feet, and opposable fingers are the most common features, leading to a so-called "lobster claw" appearance. The major feature observed is monodactyly, where the radial rays are absent with, as a rule, only the fifth digit remaining. Non-syndromic forms are usually isolated but there have been rare reports of an association with deafness. The malformation has also been observed with aniridia and Alport syndrome. Management includes surgical reduction of the malformation and orthesis. Five loci for SHFM have been mapped: SHFM1 on chromosome 7, SHFM2 on chromosome X, SHFM3 on chromosome 10, SHFM4, which is caused by mutation in the TP63 gene on chromosome 3, and SHFM5 on chromosome 2. Inheritance depends on the genetic localization: SHFM, 3 and 4 have dominant autosomal transmission (with incomplete penetrance), SHFM2 is X-linked recessively inherited. The mode of SHFM 5 transmission is unknown: recessive or dominant inheritance with incomplete penetrance have both been discussed. |