Tumor-induced osteomalacia: a case report.

Tumor-induced osteomalacia (TIO) is a rare paraneoplasic syndrome with overproduction of fibroblast growth factor 23 as a phosphaturic agent, leading to chronic hyperphosphaturia and hypophosphatemia, associated with inappropriately normal or low levels of 1,25-dihydroxyvitamin D. Diagnosis of this disease is often challenging. The following case report described a middle-aged man with symptoms of bone pain and severe muscle weakness, who was found to have TIO. The tumor responsible for the symptoms was localized on his thigh and its resection resulted in normalization of blood chemistry and complaints. Subsequent microscopic examination revealed a phosphaturic mesenchymal tumor, mixed connective tissue type. The authors reinforce the importance of recognition of this disease, as severe disability and even death can be avoided with the surgical removal of the causative tumor.