A Sinonasal Paranasal Mesenchymal Tumor Associated With Tumor-Induced Osteomalacia: A Case Report and Literature Review.

Introduction: Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome that is characterized by hypophosphatemia resulting from the leakage of renal phosphate. Due to its diverse and nonspecific clinical manifestations, the diagnosis is often delayed.

Case report: We present the rare case of a 33-year-old man with TIO who was presented with chronic bilateral hip joint pain and was initially misdiagnosed with osteonecrosis of the femoral head. He suffered from gradually increasing pain and weakness, culminating in walking only with the aid of crutches and severe limitation in daily activities. He was admitted to our hospital for a planned total hip arthroplasty. ⁶⁸Ga-DOTA-TATE positron emission tomography/computed tomography and pathology results confirmed a paranasal mesenchymal tumor. The patient was eventually diagnosed with TIO. The tumor removal led to a complete reversal of this patient's health condition, restoring his ability to walk, and no signs of recurrence after the follow-up of 1 year.

Conclusion: TIO due to a tumor of the nasal cavities and paranasal sinuses is very rare. Because of high rates of misdiagnosis and delayed diagnosis, nasal endoscopy can also be commended as a screening method for osteoporosis and hypophosphatemia in young people.