IS Case 243: Polyostotic fibrous dysplasia with fracture
Imaging Sciences URMC 2008
Publication Date: 2009-05-26
Multiple areas of increased radiotracer uptake throughout the bony skeleton including the spine, multiple ribs, left pelvis, left femur, and left tibia. There is deformity and mild expansion of some of the involved osseous structures, most notably the left femur and left tibia. Focal band of increased radiotracer activity involving the subcapital region of the left femoral neck suggestive of a fracture.
Fibrous dysplasia is a relatively common, benign skeletal disorder, typically encountered in adolescents and young adults with 75% of the cases occurring before 30 years of age. Rather than a true neoplasm, fibrous dysplasia is a developmental anomaly in which the normal medullary space of the affected bone is replaced by fibroosseous tissue. The process may affect a single bone (monostotic fibrous dysplasia) or many bones (polyostotic fibrous dysplasia). When polyostotic, all the lesions tend to occur on one side of the body. The bones most frequently involved are the long bones: femur (most common), skull, and the ribs. Polyostotic disease can be associated with abnormal skin pigmentation (ipsilateral to the osseous lesions) and endocrinopathies. The constellation of polyostotic fibrous dysplasia, skin pigmentation and precocious puberty has the eponym McCune Albright Syndrome. Mazabraud Syndrome is fibrous dysplasia associated with soft tissue myxomas.
The radiographic findings of fibrous dysplasia can be distinctive. Individual lesions can appear as a lucent area with a sclerotic rim. Medullary lesions have a "ground glass" appearance with a lack of normal trabeculation. The affected bone can be locally expanded. Rib lesions are usually expansile with a "ground glass" appearance. Calvarial lesions are usually lytic and multilocular with sclerotic margins. The proximal femur develops a characteristic shape referred to as a "shepherd’s crook" deformity associated with coxa vara and anterolateral bowing of the diaphysis similar to this case. Pathologic fractures are also seen as in this case.
On bone scans, fibrous dysplasia typically exhibits markedly increased radionuclide accumulation in both early perfusion and delayed bone imaging however is variable. Bone scans can be utilized to determine monostotic versus polyostotic fibrous dysplasia. Bone scans can also be utilized for pathologic fractures.
- Kransdorf MJ, Moser RP Jr, Gilkey FW. Fibrous dysplasia. Radiographics. 1990 May;10(3):519-37. [PMID: 2188311]