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Autosomal recessive osteopetrosis type 1 (ARO1) is an inherited condition characterized by abnormal bone formation. In most cases, symptoms of the condition first appear in infancy. Characteristic features include unusually dense bones, a high risk of bone fractures, a large head size with a prominent forehead, growth deficiency, and dental problems. The abnormal bone present in the skull may also lead to compression of nerves in the face and head, resulting in vision impairment or blindness, hearing loss, and paralysis of the facial muscles. In addition, breathing and feeding difficulties may result from narrowing of the passageways connecting the nose and throat.
The abnormal bone formation in ARO1 also affects the bone marrow, which is important for blood cell formation and immune system function. Consequently, children with ARO1 may have severe anemia, problems with immune system function that lead to an increased risk for infections, and enlargement of the liver and spleen. In addition, some affected individuals may have seizures due to low blood calcium levels. Intellectual disability (usually mild to moderate) may result from recurrent seizures and/or brain abnormalities that may occur in some individuals with ARO1.
It is currently unknown how often the condition occurs in the general population, although ARO1 is generally thought to be a rare disease worldwide. It is known, however, that ARO1 is more common in certain populations, including the Chuvash and Mari populations of Russia (1 in 3500 and 1 in 14,000, respectively), in the Middle East (~1 in 37,000), and in Costa Rica (~1 in 59,000).
The treatment for ARO1 is primarily supportive. Patients are monitored and symptoms are treated as they arise. Medical management typically includes blood transfusions and the treatment of fractures, infections, vision and hearing problems, and seizures if they develop. In addition, certain medications have been shown to slow the progression of the disease in some individuals. The only known cure for ARO1 is a bone marrow transplant early in life, although this procedure is associated with a high mortality rate.
Generally, the prognosis for children with ARO1 is poor. Most children with the condition die within the first decade of life, although early bone marrow transplantation can be curative, if successful.
Explanations of an extensive number of genetic diseases written for the public by the U.S. government's National Institutes of Health.
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