Fibrous Dysplasia Wheeless

Description: Discussion: - results from a defect is somatic mutation in the gene coding for alpha subunit of Gs, the G protein that stimulates cAMP formation; - overproduction of cAMP, causes overexpression of c-fos, which regulates proliferation and differentiation of osteoblasts and osteoclasts; - results in lesions of bone which results in a haphazard mixture of immature fibrous tissue & small fragments of immature trabecular bone; - angular deformities may result from defective mineralization of immature of immature dysplastic bone; - affected bone becomes widened and adjacent cortical bone becomes thin; - occurs typically in adolescence; - prevalence of malignant transformation (chondrosarcoma or osteosarcoma) is about 0.4 %; - sites of involvement: - rib is involved most often but any bone can be involved; - also seen in proximal femur, proximal tibia, mandible; - pathologic frx: - bone becomes deformed by multiple stress frx which may eventually lead to pathologic frx; - painful stress frxs are esp common in femoral neck; - although dysplastic bone heals at nl rate after frx, resulting callus is also dysplastic, and the disease persists; - prognosis: - progression of the disease is often erratic; - monostotic lesions: have good prognosis; - polyostotic lesions: - tend to remain more active or aggressive; - are known to occassionally undergo malignant transformation to osteosarcoma or fibrosarcoma. - Associated Conditions: - Albrights Syndrome - precocious puberty and cafe au lait pigmentation in females; - child w/ monostotic fibrous dysplasia usually has no symptoms; - polyostotic dz, which usually presents earlier, may be unilateral or widespread, affecting long bones, hands, feet, & pelvis; - prevalence of malignant transformation (chondrosarcoma or osteosarcoma) is about 4 %;