Phosphaturic mesenchymal tumour in the temporal bone – A rare presentation

BackgroundTumour-induced osteomalacia (TIO) is a rare clinical entity in which secondary osteomalacia is induced by tumour-related products. There is impaired reabsorption of phosphorus in the renal tubules and hypophosphatemia as a result of over expression of FGF-23 mRNA. Treatment of choice is considered to be total or near total resection of the tumour.Methods and resultsA 49-year-old man had experienced systemic bone pain and bilateral limb weakness for several months. He had refractory hypophosphatemia and marked elevation of serum FGF-23 level. Magnetic resonance imaging (MRI) of the lumbar spine showed a focal lesion in the left temporal bone which was hyper metabolic on positron emission tomography (PET) scan, leading to a diagnosis of TIO. He underwent lateral skull-base surgery after thorough evaluation of the tumour. After the en bloc resection, FGF-23 became gradually undetectable, phosphate reabsorption normalised, and all symptoms were resolved.ConclusionsWe present the clinical features and treatment options for this most unusual manifestation of phosphaturic mesenchymal tumour in the temporal bone.