Phosphaturic Mesenchymal Tumor: From Invisibility to Bedridden Morbidity.

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome caused by fibroblast growth factor 23 (FGF23) secreting phosphaturic mesenchymal tumors. We report a 53-year-old man with progressive osteomalacia resulting in bedridden status. Renal phosphate wasting despite normal vitamin D, intact parathormone, and renal function raised suspicion of TIO, confirmed by elevated FGF23. However, the occult tumor was localized only by Ga-68 DOTANOC wholebody PET-CT, highlighting the diagnostic challenges in TIO.