Aplasia of tibia with split-hand/split-foot deformity. Report of six families with 35 cases and considerations about variability and penetrance.

Six families with a total of 34 affected persons with the syndrome of tibial aplasia and ectrodactyly are reported. The spectrum of malformations is compared to that of 99 familial cases from the literature. The full-blown syndrome consists of bilateral aplasia of tibiae and split-hand/split-foot deformity. Additional malformations may be distal hypoplasia or bifurcation of femora, hypo- or aplasia of ulnae, and minor anomalies such as aplasia of patellae, hypoplastic big toes, postaxial and intermediate polydactyly in connection with split-hand deformity, and cup-shaped ears. The mildest visible manifestation may be hypoplastic big toes, the severest is tetramonodactyly or transverse hemimelia. This disorder is autosomal dominantly inherited. The penetrance is markedly reduced.