Familial rhizomelic dysplasia: phenotypic variation or heterogeneity?

In a consanguineous kindred of mixed ancestry in Cape Town we observed a boy with severe shortness of stature and an unusual skeletal dysplasia with marked shortness of the humeri. A male one-half second cousin had gross abnormalities of the lower limbs, which were worst in the femora, but his skeleton was otherwise virtually normal. A brother and sister of this latter individual had been similarly affected and their parents were consanguineous. The question arises as to whether two similar but separate disorders are present in this family or whether the condition in these two persons represents extreme phenotypic variability of the same autosomal recessive entity.