May involve a single bone or multiple bones. Bone
manifestations are consequences of fibrous lesions that can lead to
pathologic fractures, limping, unequal limp length, chest deformity, skull
asymmetry, leontiasis-like appearance, scoliosis. Sarcomatous degeneration
has been described in approximately 0.5% of patients. Irregular macular
dermal pigmentation can be observed. Other features can include precocious
puberty, hyperthyroidism, Cushing disease, hyperparathyroidism, and
hypophosphatemia.