Some Examples of Supernumerary Anatomical Structures in Arm and Hand Associated with Genetic Conditions such as the Ellis-Van Creveld Syndrome

Abstract

We showed some examples of supernumerary structures in lower arm and hand, by means of their presence during ontogeny and in comparative anatomy. In non-human primates and their predecessors, the presence of such supernumerary muscles as the contrahentes muscles and the extensor digitorum profundus muscle, may be quite normal, while with respect to human anatomy most of these muscle-layers disappear during ontogeny. Full persistence however, may be associated with certain genetic conditions. A specific example of supernumerary digital rays in the definitive hand, namely the Ellis-van Creveld (EVC) syndrome or postaxial polydactyly, was then discussed. First depicted in 1670, this genetic condition did persist by inheritance, in the offspring of 17th and 18th century mennonite migrants, fleeing from Switzerland and the Palatinate. Currently described in Amish and Brasilian families, this condition also occurs in Western Australian Aboriginal families.