Radiological, biochemical and hereditary evidence of two types of autosomal dominant osteopetrosis

Review of the radiographs of 34 patients with autosomal dominant osteopetrosis revealed two distinct phenotypical types. Both were strictly family-related and exhibited progressive sclerosis with aging. Descriptive, radiogrammetric and biochemical analyses were performed. Type I showed a pronounced sclerosis of the skull with an enlarged thickness of the cranial wall. The sclerosis of the skull in Type II was most striking at the base. In Type II there was a typical “Rugger-Jersey spine,” and endobones (“bone within a bone”) were seen in the pelvis. The radiogrammetric investigations of the long bones did not show any difference between the two types. Compared to normal controls, there was a normal total subperiosteal width (W), but a significant enlarged cortical thickness (C) (P < 0.01), and thus a reduced medullary cavity (M), suggesting normal bone formation and disturbed bone resorption. Serum phosphate was lower in Type I compared to Type II (P < 0.01), and serum acid phosphatase was markedly increased in Type II (P < 0.01), suggesting differences between the two types in bone mineral metabolism and structural functions of the osteoclasts. The two types may represent two different entities with the same mode of inheritance, and in both cases with affected bone resorption.