Tumor-induced osteomalacia due to a phosphaturic mesenchymal maxillary tumor

Abstract

ABSTRACT Tumor-induced osteomalacia is a rare paraneoplastic syndrome with hypophosphatemia due to renal phosphate wasting. The clinical presentation is bony pains and muscle wasting. A 23-year-old male presented to us in a wheelchair with joint pain and muscle weakness for 5 years. There was no history of a similar disease in the family. Treatment with non steroidal anti inflammatory drugs, steroids, and infliximab was unsuccessful. Positive examination findings revealed tenderness and swelling in both ankle and knee joints, tenderness in hip joints, proximal myopathy, and power grade 4/5 in the proximal leg muscles. On evaluation, he was found to have severe hypophosphatemia [serum phosphate 1.2 mg/dl], decreased renal phosphate absorption [tubular maximum for phosphate reabsorption adjusted for glomerular filtration rate (TMP/GFR) of 1.04], increased fibroblast growth factor 23 (FGF23), and decreased 1,25 dihydroxy vitamin D levels. Fluorodeoxyglucose-positron emission tomography (FDG PET-CT) revealed a left maxillary tumor. Histopathology revealed a mesenchymal tumor. Tumor excision resulted in cure of the patient’s symptoms and the normalization of serum phosphate levels and TMP/GFR.