Fibrous Dysplasia

Fibrous dysplasia is a typically benign bone lesion characterized by intramedullary fibro-osseous proliferation secondary to altered osteogenesis. First introduced by Lichtenstein and Jaffe in 1942 and originally termed Jaffe-Lichtenstein syndrome, fibrous dysplasia can occur in monostotic form (single bone) or polyostotic form (multiple bones). Fibro-osseous tissue replacing normal bone can result in complications including fractures or compression of adjacent soft tissues including neurovascular structures. Monostotic fibrous dysplasia is often an asymptomatic clinical entity. The polyostotic form often presents in childhood. Adult presentation often occurs incidentally during imaging for an unrelated indication. Fibro-osseous replacement of bone can lead to pathologic fracture, especially in weight-bearing bones or the upper extremities in athletes. Malignant transformation is rare, and remote radiation therapy has been reported as a risk factor. McCune-Albright syndrome is a relatively rare condition featuring polyostotic fibrous dysplasia (often unilateral) with skin pigmentation lesions and endocrine dysfunction (often female precocious puberty). Mazabraud syndrome is a very rare polyostotic variant that features coexistent single or multiple intramuscular myxomas.