Tumor-induced rickets-osteomalacia: an enigma

Objectives: We report a case of pediatric thoracic tumor-induced osteomalacia (TIO) causing severe hypophosphatemic rickets with delayed diagnosis and emphasize on timely management of this rare entity. Case presentation: A young boy presented with rickets since five years of age. Biochemical evaluation revealed hypophosphatemia, hyperphosphaturia, elevated alkaline phosphatase and normal calcium levels. Initially managed as hereditary hypophosphatemic rickets, he was given phosphorus supplements and calcitriol. Despite the therapy, skeletal deformities worsened requiring surgical corrections. Subsequently, he developed iatrogenic tertiary hyperparathyroidism for which he underwent total para. thyroidectomy. Later on, he was found to have fibroblast growth factor-23 secreting thoracic mass (10.5 cm in largest dimension) which was excised with significant post operative improvement. Histopathology showed phosphaturic mesenchymal tumor-mixed connective tissue variant, confirming the diagnosis of TIO. Conclusion: TIO, a correctable cause of hypophosphatemic rickets, should be considered in children presenting with hypophosphatemic rickets with evident mass on examination/imaging and in refractory cases.