Oncogenic osteomalacia caused by occult nasal mesenchymal tumor: a monster in the cave

Authors describe a case of oncogenic osteomalacia in a 35-year-old man, who presented with a 2-year history of generalized pain and progressive weakness of lower limbs, eventually became bedbound. At admission, he had severe hip pain resulting from bilateral femoral neck fractures. Laboratory investigations revealed hypophosphatemia, hyperphosphaturia, normocalcemia, elevated alkaline phosphatase and normal serum levels of parathormone and 25-hydroxyvitamin D. Serum fibroblast growth factor 23 (FGF23) level was elevated. A radiographic skeletal survey showed osteoporosis and insufficiency fractures of the femoral neck. A whole-body functional imaging failed to reveal any areas of increased activity. However, on computed tomography and magnetic resonance imaging of the head and neck region, a tumor was discovered at left nasal cavity. The tumor was surgically removed. After surgery, his symptoms were relieved and biochemical parameters normalized. We stress that careful clinical examination including nose and paranasal sinuses may be rewarding in cases with hypophosphatemic osteomalacia.