Osteogenic osteomalacia (phosphaturic mesenchymal tumour, tumour-induced osteomalacia, tumor-induced osteomalacia, tumour induced osteomalacia, tumor induced osteomalacia, TIO) is a paraneoplastic syndrome caused by tumours that excrete fibroblast growth factor 23 (FGF-23). The patients exhibit:
- Hypophosphataemia due to renal PO4 wasting.
- Inappropriately low/normal Vitamin D blood levels (presentation is as for osteomalacia, unresponsive to Vitamin D)
- Normal/evaluated FGF-23 blood levels
- A tumour often an osteosarcoma which may be initially occult