Pathogenesis of osteosclerosis in autosomal dominant osteopetrosis.

OBJECTIVE The purpose of this study was to determine if the generalized osteosclerosis seen on skeletal radiographs of patients with osteopetrosis is associated with an increase in bone density. SUBJECTS AND METHODS Five children (three girls, two boys, 6-12 years old) with autosomal dominant osteopetrosis who had sustained a fracture with minimal trauma had the density and area of cortical bone at the midshaft of the femur and the amount of cancellous vertebral bone per voxel measured by quantitative CT. Values for five children with osteopetrosis were compared with measurements for two control groups of healthy subjects matched for age, sex, Tanner stage of sexual development, race, weight, and height. RESULTS Both the area of femoral cortical bone and the amount of cancellous vertebral bone per voxel were significantly greater in the children with osteopetrosis than in the healthy children. The density of bone in the children with osteopetrosis was the same as the density in the healthy subjects. Neither sex, age, height, or weight influenced bone density, and values were similar for all 15 children. CONCLUSION The osteosclerosis depicted on skeletal radiographs of patients with osteopetrosis results from an increase in the amount of bone, not from an increase in the percentage of mineralized bone per unit volume of tissue.