Tumor-induced osteomalacia: The tumor may stay hidden!

We report the case of a patient with severe muscular and articular tenderness that caused almost complete immobility. This subject had severe hypophosphatemia due to hyperphosphaturia. Fibroblast growth factor 23 (FGF-23) was abnormally high and the diagnostic of tumor-induced osteomalacia was made. Despite multiple tests, the tumor was not localized. In this report, we discuss different possible investigations to localize the tumor. Lastly, we review the potential therapy available when tumor is not found and can thus not be excised.