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The purpose of this study was to determine the association between measures of disease severity, impairment, and ambulation ability in persons with polyostotic fibrous dysplasia (PFD). A cross-sectional sample of 81 patients (ages 5-57) with polyostotic fibrous dysplasia was evaluated as part of an ongoing study. Subjects were scored on the Skeletal Disease Burden Score (SDBS), completed a 9-minute walk test (9MW), manual muscle testing (MMT), and measurements of range of motion (ROM). Correlations between continuous variables were calculated using the Pearson correlation coefficient and ordinal variables by Spearman correlation coefficient. It was found that subjects with more severe disease walked slower than those with less skeletal disease, with the exception of the youngest subjects. Walking velocity was faster in subjects with better hip strength and range of motion and slower in those with bilateral coxa vara. Those subjects with more severe disease had less range of motion, were weaker at the hips, and more likely to have leg length discrepancy. Skeletal disease severity was associated with hip weakness, leg length discrepancy, and loss of range of motion. In most cases, findings did not differ in the presence or absence of associated endocrinopathies. Skeletal disease severity, MMT and ROM each has an impact on walking efficiency in persons with PFD. These findings suggest that treatment focused on strategies to improve or, at least, maintain hip strength and range of motion, correct leg length discrepancies and hip malalignment may help preserve ambulation ability in persons with PFD and that treatment should begin at a young age.

McCune–Albright syndrome is a genetic disorder characterized by polyostotic fibrous dysplasia, precocious puberty, and cafeau-lait spots. The main defect is a missense mutation in the GNAS1 gene, which results in the constitutive activation of the a-subunit of the Gs protein leading to overproduction of cAMP. Clinical presentation is variable due to the mosaic pattern of involvement of the tissues. Herein, we present a case of McCune–Albright syndrome (MAS) displaying the radiologic and biochemical features of Paget’s disease of bone. A 24-year-old woman was referred to our hospital due to skeletal deformities and facial dysmorphism. Her history included regular menses beginning at the age of 5 months, and bone deformities becoming evident at the age of about 5 years. Recently, she had been operated on due to a maxillary tumor; its pathological assessment yielded a diagnosis of fibrous dysplasia. On physical examination she was measured to be 90 cm in height. Facial asymmetry with depression of the left maxillary area was noted. She had extreme kyphoscoliosis and her right leg (tibia) had a bowing deformity. Routine blood chemistry showed a calcium level of 9.3 mg/dL, a phosphorus level in the lownormal range (2.9 mg/dL, normal 2.7–4.5), and a high alkaline phosphatase level (834 U/L, normal 42–98). Plasma levels of T3, T4, TSH, LH, FSH, estradiol, DHEAS-S, testosterone, free testosterone, growth hormone, prolactin, cortisol, and ACTH were all in the normal range. The parathyroid hormone level was 59.5 pg/mL (normal 9–55). Urinary hydroxyproline excretion was 392.3 mmol/mL creatinine (normal ,30). Radiological examination of the cranium revealed diffuse sclerosis of the skull base, thickening of the calvarium, and radiolucent areas (Figure 1). These changes were thought to be most compatible with Paget’s disease of bone. Both femurs showed widening of the bone shaft, ground glass appearance, and cortical thinning. Whole-body scintigram revealed dense uptake of the radiolabel in an asymmetric pattern (Figure 2). MRI scan of the sella revealed no pituitary adenoma. The presence of pathologically confirmed polyostotic fibrous dysplasia and a history of precocious puberty was considered decisive for diagnosis of MAS. The absence of cafe-au-lait spots does not exclude such a diagnosis, considering the mosaic nature of the disease. The most striking feature of the case was radiological findings closely mimicking those of Paget’s disease of bone. In the cranial radiographs, calvarial thickening, radiolucent areas resembling osteoporosis circumscripta, and sclerotic changes were considered compatible with Paget’s disease. Although these two disorders can cause thickening of the bones, X-ray findings of polyostotic fibrous dysplasia mimicking those of Paget’s disease have been emphasized very infrequently. Coexistence of both clinical situations has also been reported. Histologically, prominent osteoblasts on the surface of bone trabeculae and abnormal lamellar bone are characteristics of Paget’s disease and distinguish it from fibrous dysplasia. However, differentiating between Paget’s disease and polyostotic fibrous dysplasia should not be difficult on clinical grounds considering the very early onset of symptoms in the latter, particularly in the present case where the bony deformities had become evident at the age of about 5 years, which has not been seen in Paget’s disease. The high urinary hydroxyproline excretion and high serum alkaline phosphatase observed in our case may reflect the high bone turnover associated with polyostotic fibrous dysplasia, a feature also shared by Paget’s disease of bone. These findings suggest Address for correspondence and reprints: Dr. Sukru Palanduz, Fevzi Pasa Caddesi, Testereci Sokak, 1/10, Karagumruk, Fatih, 34230 Istanbul, Turkey. Figure 1. Lateral radiograph of the cranium showing calvarial thickening, radiolucent areas resembling osteoporosis circumscripta, and striking osteosclerosis involving particularly the skull base. Bone Vol. 24, No. 2 February 1999:157–158