Bilateral absence of the ulna in twins as a manifestation of the split hand--split foot deformity.

Bilateral absence of the ulna and ulnar rays in twin female infants are described as a manifestation of the split hand--split foot deformity (ectrodactyly). Family history revealed the father had a unilateral split hand. Given the wide variability of expression of this disorder and the availability of prenatal diagnosis, there is a need for obstetricians and pediatricians to recognize parents with this malformation and appreciate the potential for severely affected offspring.