Division of Endocrinology and Metabolism, Department of Internal Medicine, Kurume University School of Medicine, Kurume, Fukuoka, Japan.
Department of Radiology, Kurume University School of Medicine, Kurume, Fukuoka, Japan.
Am J Case Rep. 2024 Apr 13;25:e943152. doi: 10.12659/AJCR.943152.
BACKGROUND Tumor-induced osteomalacia (TIO) is a paraneoplastic syndrome caused by aberrant fibroblast growth factor-23 (FGF-23)-producing tumors. Early surgical resection is the optimal strategy for preventing TIO progression. Thus, tumor localization is a priority for successful treatment. A simple and safe examination method to identify functional endocrine tumors is essential to achieve better outcomes in patients with TIO. CASE REPORT A 64-year-old Japanese man with recurrent fractures, hypophosphatemia, and elevated alkaline phosphatase and FGF-23 levels (109 pg/mL) was admitted to our university hospital and was diagnosed with FGF23-related hypophosphatemic osteomalacia. Notably, the superficial dorsal vein in the patient's left foot exhibited a high FGF-23 level (7510 pg/mL). Octreotide and ¹⁸F-fluorodeoxyglucose (FDG) scintigraphy and systemic venous sampling revealed that the tumor in the third basal phalanx of the left foot was responsible for FGF-23 overproduction. Tumor resection resulted in a rapid decrease in serum FGF-23 levels and an increase in serum phosphorus levels. CONCLUSIONS Octreotide scintigraphy, FDG-positron emission tomography, and systemic venous sampling are the standard methods for localizing functional endocrine tumors. However, the limited availability and invasive nature of these examinations hinder effective treatment. Here, we highlight the importance of peripheral superficial blood sampling as an alternative to conventional systemic methods for confirming the presence of FGF-23-producing tumors. Clinicians should consider TIO as a potential cause of acquired hypophosphatemic osteomalacia. Furthermore, peripheral superficial vein blood sampling may be useful for confirming the localization of FGF-23-producing tumors.
肿瘤性骨软化症（TIO）是一种副肿瘤综合征，由异常成纤维细胞生长因子-23（FGF-23）产生的肿瘤引起。早期手术切除是预防 TIO 进展的最佳策略。因此，肿瘤定位是治疗成功的首要任务。找到一种简单、安全的方法来识别功能性内分泌肿瘤，对于 TIO 患者获得更好的治疗效果至关重要。
一名 64 岁的日本男性，因复发性骨折、低磷血症、碱性磷酸酶和 FGF-23 水平升高（109 pg/mL）而入住我院，被诊断为 FGF23 相关性低磷性骨软化症。值得注意的是，患者左足背浅层静脉 FGF-23 水平升高（7510 pg/mL）。奥曲肽和 ¹⁸F-氟脱氧葡萄糖（FDG）闪烁扫描和静脉系统采样显示，左足第三跖骨的肿瘤导致 FGF-23 过度产生。肿瘤切除后，血清 FGF-23 水平迅速下降，血清磷水平升高。
奥曲肽闪烁扫描、FDG-正电子发射断层扫描和静脉系统采样是定位功能性内分泌肿瘤的标准方法。然而，这些检查的可用性有限且具有侵袭性，这阻碍了有效的治疗。在这里，我们强调了外周浅层血样作为替代传统全身方法来确认 FGF-23 产生肿瘤的重要性。临床医生应将 TIO 视为获得性低磷性骨软化症的潜在病因。此外，外周浅层静脉血样采集可能有助于确认 FGF-23 产生肿瘤的定位。
