Total body scintigraphy is useful to identify and determine the extent of bone lesions, and should be performed in all patients with suspected fibrous dysplasia.Children with fibrous dysplasia in the appendicular skeleton typically present with limp, pain, and/or pathologic fractures. Frequent fractures and progressive deformity may lead to difficulties with ambulation and impaired mobility. In the craniofacial skeleton, fibrous dysplasia may present as a painless “lump” or facial asymmetry. Expansion of craniofacial lesions may lead to progressive facial deformity. In rare cases, patients may develop vision and/or hearing loss due to compromise of the optic nerves and/or auditory canals, which is more common in patients with McCune-Albright syndrome associated growth hormone excess. Fibrous dysplasia commonly involves the spine, and may lead to scoliosis, which in rare instances may be severe. Untreated, progressive scoliosis is one of the few features of fibrous dysplasia that can lead to early fatality. Bone pain is a common complication of fibrous dysplasia. It may present at any age, but most commonly develops during adolescence and progresses into adulthood. Bone marrow stromal cells in fibrous dysplasia produce excess amounts of the phosphate-regulating hormone fibroblast growth factor-23 (FGF23), leading to loss of phosphate in the urine. Patients with hypophosphatemia may develop rickets/osteomalacia, increased fractures, and bone pain. Pathophysiology
Fibrous dysplasia is a mosaic disease resulting from post-zygotic activating mutations of the GNAS locus at 20q13.2-q13.3, which codes for the α subunit of the Gs G protein-coupled receptor. In bone, constitutive Gsα signaling results in impaired differentiation and proliferation of bone marrow stromal cells.
Progressive scoliosis can generally be managed with standard instrumentation and fusion techniques. Surgical management in the craniofacial skeleton is complicated by frequent post-operative FD regrowth, and should focus on correction of functional deformities. Prophylactic optic nerve decompression increases the risk of vision loss and is contraindicated.Managing endocrinopathies is a critical component of management in FD. All patients with fibrous dysplasia should be evaluated and treated for endocrine diseases associated with McCune–Albright syndrome. In particular untreated growth hormone excess may worsen craniofacial fibrous dysplasia and increase the risk of blindness. Untreated hypophosphatemia increases bone pain and risk of fractures. See also
Cherubism
Dysplasia
McCune–Albright syndrome

References
Further reading
GeneReviews entry for Fibrous Dysplasia/McCune-Albright Syndrome


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