What is tumor-induced osteomalacia (TIO)?

Updated: Aug 10, 2020
  • Author: Horacio B Plotkin, MD, FAAP; Chief Editor: Jatinder Bhatia, MBBS, FAAP  more...
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Tumor-induced osteomalacia (TIO) is a paraneoplastic syndrome with hypophosphatemia secondary to decreased renal phosphate reabsorption, normal or low serum 1,25-dihydroxyvitamin D concentration, osteomalacia, and myopathy.

Several mesenchymal tumors of bone or connective tissue (including nonossifying fibromas, fibroangioma, and giant cell tumors) secrete a phosphaturic substance (parathyroidlike protein) that results in rickets.

The age of onset has been late childhood, adolescence, or young adulthood. The clinical characteristics are similar to those associated with familial hypophosphatemia. FGF-23 causes renal phosphate wasting in tumor-induced osteomalacia. Treatment is surgical removal of the tumor (if it can be located), with excellent results.

Burosumab (Crysvita) is a monoclonal antibody against the phosphaturic hormone FGF-23. It is indicated for X-linked hypophosphatemia in adult and pediatric patients aged 6 months or older. It is also approved for FGF-23–related hypophosphatemia in tumor-induced osteomalacia associated with phosphaturic mesenchymal tumors that cannot be curatively resected or localized in adults and pediatric patients aged 2 years or older. [12]

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