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Progressive osseous heteroplasia
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Reviewed January 2009
What is progressive osseous heteroplasia?
Progressive osseous heteroplasia is a disorder in which bone forms within skin and muscle tissue. Bone that forms outside the skeleton is called heterotopic or ectopic bone. In progressive osseous heteroplasia, ectopic bone formation begins in the deep layers of the skin (dermis and subcutaneous fat) and gradually moves into other tissues such as skeletal muscle and tendons. The bony lesions within the skin may be painful and may develop into open sores (ulcers). Over time, joints can become involved, resulting in impaired mobility.
Signs and symptoms of progressive osseous heteroplasia usually become noticeable during infancy. In some affected individuals, however, this may not occur until later in childhood or in early adulthood.
How common is progressive osseous heteroplasia?
Progressive osseous heteroplasia is a rare condition. Its exact incidence is unknown.
What genes are related to progressive osseous heteroplasia?
Progressive osseous heteroplasia is caused by a mutation in the GNAS gene. The GNAS gene provides instructions for making one part of a protein complex called a guanine nucleotide-binding protein, or a G protein.
In a process called signal transduction, G proteins trigger a complex network of signaling pathways that ultimately influence many cell functions. The protein produced from the GNAS gene is believed to play a key role in signaling pathways that help regulate the development of bone (osteogenesis), preventing bony tissue from being produced outside the skeleton.
The GNAS gene mutations that cause progressive osseous heteroplasia disrupt the function of the G protein and impair its ability to regulate osteogenesis. As a result, bony tissue grows outside the skeleton and causes the complications associated with this disorder.
Read more about the GNAS gene.
How do people inherit progressive osseous heteroplasia?
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