Objective: To describe the clinical presentation, localization modalities, and management of patients with tumor-induced osteomalacia (TIO).
Methods: We performed a retrospective analysis of case records of patients diagnosed with TIO between January 1996 and March 2010 at our institution in Mumbai, India.
Results: Nine patients (6 female and 3 male) with a mean age of 37.5 ± 17.5 years with biochemical and imaging evidence of TIO were included in the study. Overall, patients presented with proximal muscle weakness and pain. Three patients had neurofibromatosis 1, one had isolated schwannoma, and one had epidermal nevus syndrome. The mean delay in diagnosis was 7.67 years. Biochemical studies revealed normal serum calcium (mean, 9.2 ± 0.8 mg/dL), low serum phosphorus (mean, 1.36 ± 0.54 mg/dL), and low maximal tubular reabsorption of phosphorus factored for glomerular filtration rate (mean, 0.94 ± 0.49 mg/dL). Fibroblast growth factor-23 was increased in 3 of the patients without neurofibromatosis but was normal or near-normal in all the patients with neurofibromas. A fludeoxyglucose F 18 positron emission tomography (FDG PET) scan helped to localize the tumors in 4 of the 5 patients with diagnoses other than neurofibromatosis. Three patients underwent surgical excision and were cured. One patient underwent biopsy and partial excision. Histopathologic findings were suggestive of phosphaturic mesenchymal tumor, benign fibrous histiocytoma, nonossifying fibroma, and sciatic nerve schwannoma.
Conclusion: There is a well-known delay in the diagnosis of TIO. FDG PET is a useful modality for localization of tumors. Preoperative localization increases the odds for cure after surgical excision.