A 37-year-old woman with a fibrous polyostotic dysplasia (FPD) of the left femur, tibia and foot was diagnosed at 11 years of age. At the onset she presented mechanical pain of the left hip and later a stress fracture of the femur for which she was treated with surgery, pamidronate and zolendronate. Pathology confirmed the diagnosis. Phosphocalcic metabolism was normal. X-rays (Fig. 1) showeda left femurwitha «sheperd’s staff »deformity, a thin bone cortex and expansive radiolucent lesions. The left tibia (Fig. 2) was curved and had a thin cortex. Feet (Fig. 3) were thickened at the first right metatarsal and phalange with radiolucent and sclerotic areas. A computed tomographyof the tibia (Fig. 4) observed a ground glass matrix, with heterogeneous intramarrow images. FPD is a rare anomaly of skeletal development. A mutation in the GNAS1 gene has been detected,1 producing alterations in osteoplastic maturation and abnormal fibrous tissue deposit.2 There are two variants: monostotic and polyostotic.3 Lesions are localized on the epiphysis, metaphysis or diaphysis. Themonostotic variant is more prevalent, diagnosed during the patient’s youthand less symptomatic. It affects the ribs, femur, tibia, jawbone and humerus.4 The polyostotic form is observed in 30% of cases. It is usually diagnosed during the patients’ infancy. It affects the cranium, face, pelvis, spine and shoulder. It is associated to the McCune-Albright syndrome in 2% of cases (FPD, skin pigmentation and early puberty).2 It leads to dysmetria, gait abnormalities, mechanical pain and stress fractures.5 FPD diagnosis is radiological, rarely requiring a bone biopsy. The prognosis depends on the extension and degree of bone affection, age at