Tumour-induced osteomalacia

Tumour-induced osteomalacia (TIO) is a rare paraneoplastic syndrome caused by increased production of fibroblast growth factor 23 (FGF-23). A 45-year-old man presented to us with progressive weakness over 2 years along with recurrent fractures with minimal trauma. His FGF-23 was found to be above the normal range and DOTATATE positron emission tomography (PET) scan showed a well-defined enhancing soft tissue density involving the left posterior ethmoid with extension to the spheno-ethmoidal recess and sphenoid sinus ostium. He underwent endoscopic sinus surgery and excision of the tumour. Histopathological examination showed features of phosphaturic mesenchymal tumour-mixed connective tissue type. Postoperatively the serum phosphorus level increased from day 1 and reached the normal value of 2.5 mg/dl on day 3. He was discharged and continued on oral calcium and vitamin D3. Gradually his myalgia improved and he started walking independently over the next 1 month. The mean delay from symptom onset to treatment in our patient was 2 years and 5 months. Timely diagnosis and meticulous follow-up are necessary for the management of patients with this rare disorder.