Tumor-induced osteomalacia originating from the temporal bone: a case report.

Abstract

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. 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. We discuss the clinical features and treatment options for this rare disease.