Venous sampling for fibroblast growth factor-23 confirms preoperative diagnosis of tumor-induced osteomalacia.
Tumor-induced osteomalacia (TIO) is a paraneoplastic disorder characterized by hypophosphatemia, phosphaturia, inappropriately low serum levels of 1,25-dihydroxyvitamin D for hypophosphatemia, and skeletal undermineralization. Patients with TIO suffer from severe muscle weakness and pain. Because surgical removal of the responsible tumors is the only satisfactory treatment for TIO, identification of the tumors is clinically essential. However, because they are predominantly slow-growing neoplasms of benign mesenchymal origin, localization of the responsible tumors is often very difficult. Moreover, even if a tumor is found in a patient with hypophosphatemic osteomalacia, we have had no way to know that the tumor is actually causing the disease. Fibroblast growth factor-23 (FGF-23) was recently identified as a causative factor for TIO and was shown to induce renal phosphate wasting. We have recently shown that the circulatory FGF-23 level was high in a patient with TIO and rapidly decreased after removal of the responsible tumor. For the first time, we describe a patient with adult-onset hypophosphatemic osteomalacia in whom a clinical diagnosis of TIO was confirmed before surgical removal of the tumor by localizing the responsible tumor using venous sampling for FGF-23 together with magnetic resonance imaging. This combinatorial procedure would be clinically useful for sporadic cases of hypophosphatemic rickets/osteomalacia.
Division of Endocrinology and Nephrology, Department of Medicine, University of Tokyo School of Medicine, Japan. takeuchi-tky@umin.ac.jp
Yasuhiro
Y
Takeuchi
Hisanori
H
Suzuki
Sayoko
S
Ogura
Rie
R
Imai
Yuji
Y
Yamazaki
Takeyoshi
T
Yamashita
Yoshinari
Y
Miyamoto
Hiroshi
H
Okazaki
Kozo
K
Nakamura
Kazuhiko
K
Nakahara
Seiji
S
Fukumoto
Toshiro
T
Fujita
D000008:Abdominal Neoplasms / Q000150:complications* / Q000601:surgery; D000328:Adult; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood*; D006801:Humans; D017674:Hypophosphatemia / Q000209:etiology; D007264:Inguinal Canal / Q000601:surgery; D008279:Magnetic Resonance Imaging; D008297:Male; D010018:Osteomalacia / Q000175:diagnosis* / Q000209:etiology*; D014680:Veins
C000717427:FGF23 protein, human; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23