What is oncogenic osteomalacia?
Oncogenic (tumor-induced) osteomalacia is a rare cause of osteomalacia in adults and rickets in children. It is most commonly caused by benign (rarely malignant) endodermal or mesenchymal tumors that secrete FGF-23 and other proteins that can cause hypophosphatemia. Serum FGF-23 is a known inhibitor of phosphate transport in the renal tubule and the 1-alpha-hydroxylase enzyme in the kidney; it can be measured in serum in commercially available assays.
Affected patients present with myalgias and bone pain due to osteomalacia. Laboratory features include low serum phosphate, high serum alkaline phosphatase, high urinary phosphate, high FGF-23 level, and low 1,25 (OH) 2 vitamin D. The tumors tend to be small and are best localized by Gallium-68 DOTATATE positron emission tomography scanning. Surgical removal of the tumor is curative.