Fibrous<unk>  of the right zygomatic<unk>  (left). Corresponding T2-weighted MRI (left) and CT (right) of the same patient. Fibrous<unk>  is a mosaic disease that can involve any part or combination of the craniofacial, axillary, and/or appendicular skeleton. The type and severity of the complications therefore depend on the location and extent of the affected skeleton. The clinical spectrum is very broad, ranging from an isolated, asymptomatic monostotic lesion discovered incidentally, to severe disabling disease involving practically the entire skeleton and leading to loss of vision, hearing, and/or mobility. Individual<unk>  lesions typically manifest during the first few years of life and expand during childhood. The vast majority of clinically significant<unk>  lesions are detectable by age 10 years, with few new and almost no clinically significant<unk>  lesions appearing after age 15 years. Total body scintigraphy is useful to identify and determine the extent of<unk>  lesions, and should be performed in all patients with suspected fibrous<unk> . Children with fibrous<unk>  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<unk>  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<unk>  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<unk>  that can lead to early fatality.<unk>  pain is a common complication of fibrous<unk> . It may present at any age, but most commonly develops during adolescence and progresses into adulthood.<unk>  marrow stromal cells in fibrous<unk>  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<unk>  pain. Micrograph of fibrous<unk>  (right) juxtaposed with unaffected<unk>  (left). H&E stain.
Fibrous dysplasia of bone
Fibrodysplasia ossificans progressiva
Osteofibrous dysplasia
Giant-cell tumor of bone
Osteoma cutis
Myositis ossificans
Diffuse idiopathic skeletal hyperostosis
Osteitis fibrosa cystica