Tumor-induced osteomalacia (TIO), a rare paraneoplastic syndrome, is caused by fibroblast growth factor 23 (FGF23)-secreting mesenchymal tumors.[1] FGF23 overproduction inhibits Na-P cotransporters in the renal proximal convoluted tubule, impairing phosphate reabsorption and leading to phosphate diuresis. This evidence concerns the gene FGF23 and mesenchymal cell neoplasm.