Unveiling the mystery: A rare case of hypophosphatemia

Abstract

Tumor-induced osteomalacia (TIO) or oncogenic osteomalacia is a rare paraneoplastic syndrome characterized by an autonomous and unregulated production of fibroblast growth factor 23 (FGF23), which promotes urinary phosphorus wasting and systemic hypophosphatemia. Clinical manifestations are often nonspecific and unfortunately, the syndrome is underdiagnosed or recognized late. Hypophosphatemia is often attributed to other more common etiologies and is often not identified at all, leading to a more advanced disease at the time of diagnosis. Thus, it is necessary to have a high index of suspicion when evaluating hypophosphatemia, as early identification and intervention of TIO can prevent or reverse osteomalacia and lead to an expedited investigation of a culprit neoplasm. We describe a case of TIO associated with established mesothelioma and outline the diagnostic steps taken that ultimately taken to reach a final diagnosis. While rare, this condition should not be missed by the conventional nephrologist, who routinely measures phosphorus levels in their patients, and thus, we provide a framework to follow in the assessment of hypophosphatemia and the ultimate diagnosis of TIO.