Diseases & Conditions


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Osteogenesis Imperfecta


Osteogenesis imperfecta is a group of disorders of bone formation that make the bones abnormally fragile.

Typical symptoms include weak bones that break easily. The diagnosis is based on x-ray studies. The type that occurs in infancy is lethal. Certain drugs and injections can help strengthen bones.

Osteogenesis imperfecta (OI) is the best known of a group of disorders that disturb bone growth; these disorders are called osteodysplasias. In OI, synthesis of collagen, one of the normal components of bone, is impaired. The bones become weak and fracture easily. There are several types of OI.

OI can range from mild to severe. Most people with OI have fragile bones, and about 50% have hearing loss. Infants with severe OI are usually born with many broken bones. The skull may be so soft that the brain is not protected from pressure applied to the head during childbirth. This most severe type is lethal, and the infant can die either before childbirth or within the first few days or weeks of life. Another severe form of OI, which is not lethal, causes bones to often break after very minor injuries, usually when the child begins to walk. Children with moderate OI may sustain few broken bones during childhood and even fewer after puberty, when bones strengthen. Sometimes heart or lung diseases develop in children with OI.

X-ray studies may show abnormal bone structure that suggests OI. The removal of a sample of skin for examination under a microscope (biopsy) or to grow a type of connective tissue cells (fibroblasts) in a culture dish is performed to confirm the diagnosis. The most severe and lethal form of OI can be detected in pregnant women by an ultrasound. A test called audiometry is performed often throughout childhood to monitor hearing.

Treatment

Bisphosphonate drugs (such as pamidronate Some Trade Names AREDIA or alendronate Some Trade Names FOSAMAX ) may strengthen bones. Growth hormone injections can also help children with certain types of OI. Treatment of broken bones is similar for children with OI as for children who do not have the disorder. However, broken bones can become deformed or fail to grow. As a result, body growth can become permanently stunted in children with many broken bones, and deformities are common. Bones may require stabilization with metal rods (intramedullary rods). Physical therapy and occupational therapy help prevent fractures and improve function. Taking measures to avoid even minor injuries can help prevent fractures.

Last full review/revision February 2008 by Frank Pessler, MD, PhD; David D. Sherry, MD

Source: The Merck Manual Home Edition