Genetics and limb deficiencies.

The majority of cases of limb deficiencies are sporadic with no recurrence risk. This is particularly true for terminal transverse defects. Some terminal transverse defects, such as acheiropody, however, are part of genetic syndromes. There is a variety of radial defects, some of them autosomal dominant, some autosomal recessive, some due to chromosomal aberrations, and some sporadic. It is usually possible to indicate the mode of inheritance of radial defects by paying close attention to morphologic details of the limb malformation and to accompaying malformations. Most ulnar and fibular defects are sporadic, yet there are some genetic syndromes in which absence of ulna or fibula may occur. There are several domonant types of splithand-splitfoot. Classification is difficult, however, because of the great intrafamilial variability. Atypical nonhereditary splithand is usually unilateral. Most cases of unilateral total syndactyly probably belong to the same category.