Fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder in which normal bone forms in abnormal locations, such as in muscles, tendons, ligaments and other connective tissues. The body produces not just too much bone, but an extra skeleton that immobilizes the joints of the body. These lesions slowly replace the body's muscles with normal appearing bone. Any attempt to remove the extra bone results in even more robust bone formation. There is no effective treatment.

Scientists do not yet know why the disease is active some times and dormant at other times. FOP is a genetic disease and can be inherited, though most cases arise from unaffected parents. The disease is most likely the result of a damaged gene or genes.

FOP has a prevalence of approximately one in two million, affecting approximately 2,500 people worldwide.