Oncogenic Osteomalacia: The Search, Treatment, and Cure of a Debilitating Tumor

ABSTRACT Objective To present a rare case of oncogenic osteomalacia, describe the breadth of potential clinical symptoms, and review the underlying pathophysiology of this disorder. Methods We report a case of oncogenic osteomalacia cured by surgical resection of a mesenchymal tumor. Results A 48-year-old, wheelchair-dependent man presented to a tertiary care academic hospital with progressive back pain and diffuse weakness. Biochemical evaluation revealed elevated alkaline phosphatase, marked hypophosphatemia, phosphaturia, vitamin D deficiency, and elevated fibroblast growth factor 23, results that are concerning for oncogenic osteomalacia. Subsequent imaging showed extensive loss of vertebral height, numerous fractures, and ultimately identified an area suspicious for tumor in the right mandible, with concurrent uptake on octreotide scan. Segmental resection of the right mandible revealed a calcifying mesenchymal tumor. Following surgery there was a normalization of biochemistries and dramatic improvement in the patient's symptoms. Conclusion Oncogenic osteomalacia is a rare and often confounding diagnosis. Identification may be aided by the relatively recently characterized hormone fibro-blast growth factor 23. Identification of this paraneoplastic syndrome is critical, as surgical intervention has curative potential for possible debilitating symptoms.