OSTEOPETROSIS

Osteopetrosis is a rare hereditary bone disorder that presents in one of three forms: osteopetrosis tarda, osteopetrosis congenita and ''mar ble bone'' disease. Osteopetrosis tarda, the benign form, presents in adulthood while the two more malignant variants, osteopetrosis congeni ta and marble bone disease, present in infancy and childhood, respecti vely. In all three farms, the main features are pathologic alteration of osteoclastic bone resorption and thickening of cortical and lamella r bones. Osteopetrosis tarda is usually discovered accidentally on rou tine radiographs and is often asymptomatic; however, patients may pres ent because of related degenerative joint disease. Osteopetrosis conge nita results in bone marrow failure and is almost always fatal. Marble bone disease causes short stature, cerebral calcification and mental retardation. Bone marrow transplant is the only chance for survival in patients with osteopetrosis congenita.