On the inheritance of the split hand/split foot malformation

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Abstract
Analysis of families with non‐syndromal split hand/split foot (SHSF) confirms the existence of 2 distinct entities, most probably caused by at least 2 different autosomal dominant genes. In the families in which the SHSF malformation is non‐syndromal and limited to the hands and feet (type I), the pattern of inheritance is of a regular autosomal dominant gene with a high penetrance (96%). In families in which at least one individual has other limb malformations and SHSF (type II), the transmission is often unusual. In most families, the gene is non‐penetrant, sometimes for generations, before the birth of the first affected individual. Thereafter, among the descendants of affected individuals, the penetrance is reduced (66%), suggesting the possible existence of another gene which controls the appearance of the clinical manifestations. The possibility that SHSF associated with other limb malformations is a disorder caused by trinucleotide repeat instability is raised.