背景和目的：非典型股骨骨折(AFF)為長期以抗骨吸收藥物治療骨質疏鬆相關的嚴重不良事件。過往文章多報導與AFF發生前長期使用雙膦酸鹽相關的前驅髖痛；前驅期亦可以MRI證明骨髓水腫。然地諾單抗是一種生物抗骨吸收劑；其與AFF前驅之相關特色尚未被明確描述。方法：本報告回顧分析一例68歲家庭主婦長期使用地諾單抗後發生AFF的病歷；雙膦酸鹽未開立處方亦未曾使用。結果：本例展示長期使用地諾單抗可於AFF前驅期發生骨髓水腫；此篇記錄從開始使用到發生AFF及其後續之臨床過程。結論：本病例報告強調早期發現並及時調整用藥的重要。儘管患者因缺乏預防而經歷AFF，本報告目的是提高認識；通過及時調整藥物應能預防AFF。

Background and Purpose: Atypical femoral fracture (AFF) is a severe adverse event associated with long-term use of antiresorptive agent for pharmacological treatment of osteoporosis. Many previously published articles had reported prodromal hip pain associated with long-term use of bisphosphonates before occurrence of AFF; additionally, bone marrow edema might also be demonstrated using MRI during the prodromal phase. However, denosumab, a biological antiresorptive agent, is not yet as well characterized regarding its association with prodromal phase of AFF. Methods: This report retrospectively reviewed a case of 68-year-old housewife experiencing AFF after long-term use of denosumab; bisphosphonates were never prescribed and were never used. Results: This is a case to demonstrate that bone marrow edema can occur during the prodromal phase of AFF with long-term use of denosumab; clinical course from the start of its usage until occurrence of AFF and its sequela were captured. Conclusion: In this case report, crucial importance of early detection along with timely adjustment of medication is emphasized. Although the patient reported had experienced AFF due to lack of prevention, the purpose of this case report is to raise the awareness that AFF can be prevented with timely adjustment of medications.