Fibrous dysplasia of bone

Fibrous dysplasia is a very rare nonhereditary genetic disorder where normal bone and marrow is replaced with fibrous tissue, resulting in formation of bone that is weak and prone to expansion. As a result, most complications result from fracture, deformity, functional impairment, pain, and the impingement of nerves. Disease occurs along a broad clinical spectrum ranging from mostly asymptomatic incidental lesions, to severe disabling disease. Disease can affect one bone (monostotic), multiple (polyostotic), or all bones (panostotic) and may occur in isolation or in combination with café au lait skin macules and hyperfunctioning endocrinopathies, termed McCune–Albright syndrome. More rarely, fibrous dysplasia may be associated with intramuscular myxomas, termed Mazabraud's syndrome. Fibrous dysplasia is very rare, and there is no known cure. While fibrous dysplasia is not itself a form of cancer, in severe cases it may undergo a malignant transformation into cancers such as osteosarcoma or chondrosarcoma, so some clinicians may regard it as precancerous rather than benign.