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Fibrous dysplasia | |
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Micrograph showing fibrous dysplasia with the characteristic thin, irregular bony trabeculae and fibrotic marrow space. H&E stain. | |
Specialty | Medical genetics ![]() |
Symptoms | Bone pain, bone deformities, local swelling |
Complications | Bone fractures |
Usual onset | Adolescence or early adulthood (monostotic), before age 10 (polyostotic) |
Types | Monostotic (75–80% of cases),[1] polyostotic, panostotic |
Causes | Mutations of GNAS locus |
Frequency | 1 in 5,000 to 10,000[1] |
Fibrous dysplasia is a very rare[2] 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.[3] 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)[4][5] and may occur in isolation or in combination with café au lait skin macules and hyperfunctioning endocrinopathies, termed McCune–Albright syndrome.[3] More rarely, fibrous dysplasia may be associated with intramuscular myxomas, termed Mazabraud's syndrome.[6] Fibrous dysplasia is very rare, and there is no known cure.[2] 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.