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Albers-Schönberg osteopetrosis is a sclerosing disorder of the skeleton characterized by increased bone density that classically displays the radiographic sign of ``sandwich vertebrae`` (dense bands of sclerosis parallel to the vertebral endplates). The prevalence is estimated at 1:20,000. The disease typically has onset in late childhood or adolescence. The main manifestations are confined to the skeleton, including fractures, scoliosis, hip osteoarthritis and osteomyelitis, particularly affecting the mandible in association with dental abscess or caries. Cranial nerve compression is a rare but important complication, with hearing and visual loss affecting around 5% of individuals. Moderate bone marrow failure is described occasionally. The disease is caused by heterozygous mutations in the chloride channel 7 (ClCN7) gene and is transmitted in an autosomal dominant manner. Diagnosis is based on clinical findings and largely depends on the radiographic appearance of the skeleton. Genetic testing is available and can be used to confirm the diagnosis. Differential diagnosis includes other subtypes of osteopetrosis, fluorosis, beryllium, lead and bismuth poisoning, myelofibrosis, Paget`s disease (sclerosing form) and malignancies (lymphoma, osteoblastic cancer metastases) (see these terms). Genetic counseling should be offered to families. Each child of an affected individual has 50% risk of being affected. The parents of the proband should be carefully evaluated for signs of osteopetrosis, including radiographic studies of the skeleton. At present, there is no effective medical treatment for osteopetrosis. Management is supportive and aims at providing multidisciplinary surveillance and symptomatic treatment. Clinical manifestations may worsen over time but life expectancy is usually normal.
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