Endocrinol Metab > Volume 22(2); 2007 > Article
Journal of Korean Endocrine Society 2007;22(2):142-148.
DOI: https://doi.org/10.3803/jkes.2007.22.2.142    Published online April 1, 2007.
A Case of Tumor-induced Osteomalacia with Elevated Fibroblast Growth Factor-23.
Hae Sung Kim, Hyun Seung Jung, Hee Jung Kim, Sung Yeon Kim, Sang Wan Kim, Chan Soo Shin, Chong Jai Kim, Seong Yeon Kim
1Department of Internal Medicine, Seoul National University College of Medicine, Korea.
2Department of Pathology, Seoul National University College of Medicine, Korea.
3The Hormone Research Center, Seoul National University Hospital Clinical Research Institute, Korea.
Tumor-induced osteomalacia (TIO), a paraneoplastic disease, is characterized by hypophosphatemia, and caused by renal phosphate wasting inappropriately, normal or decreased 1, 25(OH)2D3 production, and defective calcification of cartilage and bone. Because the removal of the responsible tumor normalizes phosphate metabolism, unidentified humoral phosphaturic factors (phosphatonin) are believed to be responsible for this syndrome. These factors include fibroblast growth factor (FGF)-23, secreted frizzled-related protein-4 and matrix extracellular phosphoglycoprotein. However, no case of TIO producing FGF-23 has been clearly reported in Korea. Herein, a case of TIO producing FGF-23 in a 45-year-old woman is reported. The patient presented with a large tumor on her buttock, with severe bone and muscle pain. A histological examination of the tumor revealed a mixed connective tissue tumor, consisting of deposition of calcified materials and surrounding primitive spindle cells, with prominent vascularity. Whether FGF-23 is a secreted factor, as well as its levels of expression in tumors were investigated. An immunohistochemical study showed the tumor cells to be FGF-23 positive. Furthermore, the levels of serum FGF-23 were extremely high and an RT-PCR analysis, using total RNA from the tumor, revealed the abundant expression of FGF-23 mRNA. After removal of the tumor, all the biochemical and hormonal abnormalities disappeared, with marked symptomatic improvement.
Key Words: Fibroblast growth factor-23, Tumor-induced osteomalacia

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