Osteopetrosis

A 30-year-old man presented to the emergency department with new-onset seizures. His past medical history included loss of vision for 1 year, deafness, and osteomyelitis of the mandible.

The patient was short in stature, alert, and oriented. His head showed frontal and parietal bossing with proptosis. A chest film, pictured here, revealed increased density of the ribs and the vertebrae. Osteopetrosis was diagnosed.

Osteopetrosis, or Albers-Schnberg disease or marble bones, is a genetic disorder characterized by a defect in bone resorption. In its most severe form, the disease is seen in infancy and is almost always fatal; a milder form may occur in adults as well as in children.

Undiagnosed osteopetrosis, particularly in adults, may be revealed in roentgenograms taken for other reasons. Histologic changes causing uniformly dense sclerotic bone, often with no distinction between the cortical and cancellous regions, are apparent in the x-ray films of patients with this condition. Long bones usually are involved, with increased density along the entire shaft. Typically, the metaphyses appear clubbed or splayed. Neurologic abnormalities caused by the encroachment on cranial nerves include optic atrophy, nystagmus, papilledema, exophthalmos, and impaired extraocular muscle function. Facial paralysis and deafness are common.

Persons with osteitis fibrosa associated with hyperparathyroidism and osteomalacia associated with renal tubular dysfunction, as well as some patients with hypothyroidism, Paget's disease, lymphoma, multiple myeloma, or renal osteodystrophy, may have increased bone density. In osteopetrosis, the denser bone mass usually results from an excessive amount of mineral relative to the matrix. Consider osteopetrosis in the differential whenever increased bone density is revealed on a roentgenogram.