Phosphaturic Tumor-Induced Osteomalacia

Tumor-induced osteomalacia (TIO) is a rare complication of certain tumors involving the skeletal bones, mainly in the lower extremities and rarely the spine, that can cause skeletal abnormalities, osteopenia, and osteoporosis. The etiology of these tumors is unknown, and they are considered benign tumors that usually localize in bone or soft tissue anywhere in the body. Symptoms are nonspecific and vague, which causes a delay in diagnosis. These tumors produce fibroblast growth factor-23, which causes hypophosphatemia due to renal wasting of phosphate and inhibits vitamin D3 activation, resulting in osteomalacia. The majority of these tumors are osteoblastic and rarely osteolytic. A PET scan can detect the location and diagnose these tumors. Surgical resection, when feasible, is the treatment of choice and can lead to improvement, resolution of symptoms, and correction of hypophosphatemia. Patients usually present with a wide variety of nonspecific complaints. This case report presents an unusual presentation of TIO from a phosphaturic mesenchymal tumor involving the left acetabulum.