BACKGROUND: Tumor-induced osteomalacia (TIO) is a rare clinical entity in which secondary osteomalacia is induced by tumor-related products. Fibroblast growth factor 23 (FGF-23) mRNA is overexpressed in the tumor tissue, leading to impaired reabsorption of phosphorus in the renal tubules and hypophosphatemia. Curative treatment is considered to be total resection of the tumor. METHODS AND RESULTS: A 53-year-old woman had experienced systemic bone pain and muscle weakness for several years. She had refractory hypophosphatemia and marked elevation of serum FGF-23 level. Whole body imaging eventually revealed a hypervascular mass in the right temporal bone, leading to a diagnosis of TIO. She underwent skull-base surgery after embolization of the tumor. After the en bloc resection, FGF-23 became undetectable, phosphate reabsorption normalized, and all symptoms resolved. CONCLUSIONS: We discuss the clinical features and treatment options for this rare disease.
BACKGROUND:Tumor-induced osteomalacia (TIO) is a rare clinical entity in which secondary osteomalacia is induced by tumor-related products. Fibroblast growth factor 23 (FGF-23) mRNA is overexpressed in the tumor tissue, leading to impaired reabsorption of phosphorus in the renal tubules and hypophosphatemia. Curative treatment is considered to be total resection of the tumor. METHODS AND RESULTS: A 53-year-old woman had experienced systemic bone pain and muscle weakness for several years. She had refractory hypophosphatemia and marked elevation of serum FGF-23 level. Whole body imaging eventually revealed a hypervascular mass in the right temporal bone, leading to a diagnosis of TIO. She underwent skull-base surgery after embolization of the tumor. After the en bloc resection, FGF-23 became undetectable, phosphate reabsorption normalized, and all symptoms resolved. CONCLUSIONS: We discuss the clinical features and treatment options for this rare disease.