[Rickets/Osteomalacia. Diagnosis of tumor-induced osteomalacia.]

Tumor-induced osteomalacia is a fibroblast growth factor 23(FGF23)-related hypophosphatemic disorder caused by FGF23 producing tumor. TIO represents bone pain, fracture/pseudofracture, muscle weakness, etc which could lead the patient bedridden. Serum phosphate level of these patients is low with concomitant inappropriately elevated FGF23 level. Surgery is the only radical treatment method, but localization of the causative tumor could be challenging. Functional imaging is performed to detect FGF23 producing tumor, such as somatostatin receptor scintigraphy, somatostatin receptor PET/CT and systemic FGF23 venous sampling. Because prolonged hypophosphatemia would develop irreversible complications, early accurate diagnosis and tumor localization are desirable for these patients.