Bone Abstracts

X-linked hypophosphatemic osteomalacia (XLH) is an inherited skeletal disorder. The pathogenesis of the disease is fibroblast growth factor 23 (FGF23) induced renal phosphate wasting, hypophosphatemia and inappropriate lower 1, 25-dihydroxy-vitamin D₃ concentration, which lead to impaired bone mineralization. There are only a few studies focus on phenotype of XLH patients in adulthood. Therefore, this cross-sectional study systematically described anthropometric, clinical, biochemical and radiological features in adult XLH patients. The study was approved the Department of Scientific Research of Peking Union Medical College Hospital. Adult XLH patients were characterized by short stature (male, 143.7±8.56 cm; female, 140.8±7.55 cm), symptomatic at presentation with skeletal pains, the most frequent sites were knees (34/47, 72.3%), back (27/47, 67.5%), hip (14/47, 29.8%), ankles (11/47, 23.4%), and shoulder (9/46, 19.6%). All subjects had experienced dental problems, 38/46(82.6%) had spontaneous tooth decay, and 35/46 (76.1%) undergo dedentition, while peridental abscess presented in 35/46(76.1%) patients. Almost all the patients had hypophosphatemia (38/42, 90.48%), which were associated with hyperphosphaturia (26.32±16.62 mmol/24h). Half (19/38, 50%) of the patients revealed elevated ALP (127.05±65.05 U/l). Serum parathyroid hormone levels were elevated (93.34±51.71 pg/ml) in 30/42 (71.43%). The radiological spectrum illustrated wide spread distribution of bone deformation, containing lumbar and thoracic vertebra deformation(15/40), flexural deformation of femur (26/40), deformation of pelvis(23/40) and enthesopathy (21/40). Severe and prevalent degenerative joint disease in hip (75%) and knee (62.5%) were observed, and were associated with age and gender. Fracture risk of XLH patients may associate with but not restricted to BMD. Lower sitting height may relate to fracture risk (P=0. 036, OR=0.602). In conclusion, this is the largest study investigating clinical spectrum of adult XLH patients, proposed rarely reported radiologic characters, and analyzed the possible influence factors associated with fracture event.