Tumor-induced osteomalacia (TIO) is a rare but potentially curable disease. It is caused by excessive
renal clearance of phosphate induced by a substance secreted from the tumor. Here, the authors report a Thai
patient who presented with multiple pathologic fractures, low serum phosphorus, and low tubular maximum
reabsorption of phosphorus/glomerular filtration rate (TmPO4/GFR). The clinical, biochemical and bone
abnormalities improved 6 months after the surgery. Two years follow-up showed no recurrence of the disease.
Physicians should be aware of this condition when encountering with adult onset osteomalacia.

Keywords: Tumor-induced osteomalacia, Oncogenic osteomalacia, Hypophosphatemic ricket, Hemangiopericytoma,
Fibroblast growth factor 23