[Oncogenic osteomalacia: the role of the phosphatonins. Diagnostic usefulness of the Fibroblast Growth Factor 23 measurement in one patient].

Introduction: Oncogenic osteomalacia (OO) is a rare paraneoplastic syndrome characterized by severe hypophosphatemia induced by phosphaturic factors which are secreted by some tumors of mesenchymal origin. Fibroblast Growth Factor 23 (FGF-23) belongs to this family. Measurement of FGF-23 might improve the diagnosis of OO.

Exegesis: We report the case of 71-year-old Caucasian man who had a history of severe osteomalacia with multiples fractures and extreme hypophosphatemia with hyperphosphaturia and normal serum calcium level. Serum FGF-23 was 199 RU/ml (N < 100 RU/ml). The tumor, detected by F-18 FDG PET/CT SCAN was localized in the mandible. Surgical removal of the tumor relieved all symptoms with normalization of serum phosphate levels within 3 days after surgery.

Conclusion: We conclude that FGF-23 measurement is likely to be of considerable importance for facilitating early diagnosis of OO.