Namaqualand hip dysplasia: an autosomal dominant entity.

A unique inherited skeletal disorder has been identified in 45 persons in five generations of a kindred of mixed ancestry in South Africa. Discomfort in the hip joints develops in childhood and the course is progressive, with handicap in middle age. General health is good, height is not reduced by any significant degree, and there is no nonskeletal involvement. The major changes are in the femoral capital epiphyses, which are flattened and fragmented; secondary degenerative arthropathy develops at a later stage. Platyspondyly of variable but mild degree is present in about 60% of affected persons. Other minor changes, including iliac exostoses, are present occasionally. Pedigree data indicate autosomal dominant inheritance, with a reasonably consistent phenotypic expression. In view of the geographic distribution of this condition we propose the designation "Namaqualand hip dysplasia" (NHD).