Bone densitometry observations of osteopetrosis in response to bone marrow transplantation.

Spinal bone density was measured in eight patients with osteopetrosis to assess the natural history of the disease and to monitor the response to therapy. Quantitative computed tomographic scans of the lumbar vertebra were obtained in seven patients, and dual photon absorptiometric scans were obtained when the technique became available. Six children were afflicted with the infantile malignant recessive condition and two with the less severe dominant condition. In all cases, bone densitometry values ranged from four to five times higher than the mean for normal age and gender-matched controls. In four children with recessive osteopetrosis, quantitative computed tomographic and dual photon absorptiometric scans showed an excellent correlation (R = 0.93) between the methods. Quantitative computed tomographic values ranged from 597 to 730 mg/cm3 (mean = 655 mg/cm3) in children with osteopetrorickets and from 901 to 1000 mg/cm3 (mean = 980 mg/cm3) in the same children when the rickets was cured. In two children treated with bone marrow transplantation, bone densitometry values returned to normal within three years. Bone densitometry provides a safe and noninvasive method for observing the natural history and therapeutic response of the osteopetrotic syndromes.