有許多病因會造成雙下肢水腫，心臟、肝臟、腎臟等相關疾病首先需被排除。本案例為一位罹患甲狀腺亢進的59歲女性、規則服用丙硫氧嘧啶（Propylthiouracil, PTU）兩年，以雙下肢水腫為最初表現，伴隨有血尿、蛋白尿及腎功能損傷，初始臆測是不明原因的腎絲球腎炎，經檢驗發現抗嗜中性球細胞質抗體（Antineutrophil Cytoplasmic Autoantibodies, ANCA）呈陽性反應， 最終透過腎臟切片，證實為PTU相關ANCA血管炎，予以停止PTU、給予類固醇治療後，腎功能獲得改善。針對此類個案無法以症狀及檢驗檢查確立診斷時，需安排被侵犯部位的切片檢查來協助診斷，當確定是藥物相關ANCA血管炎時， 應立即停藥，避免造成致命性的傷害。

Many diseases may cause bilateral lower extremity edema. Diseases related to the heart, liver, and kidney shall be excluded first. The case of this study was a women aged 59 years with hyperthyroid­ism. The patient regularly took propylthiouracil (PTU) for 2 years. Bilateral lower extremity edema emerged as the first symptom, followed by hematuria, proteinuria, and impaired kidney functions. Initially, the medical team assumed the cause was glomerulonephritis with an unknown cause. After examination, the team discovered the patient was antineutrophil cytoplasmic autoantibodies (ANCA) positive. Through kidney biopsy, the team confirmed that the cause was PTU-related ANCA vascu­litis. Therefore the delivery of PTU was discontinued, and steroid treatment was administered. The patient’s kidney functions gradually improved. In similar cases where diagnosis cannot be confirmed through symptom interpretations or general examinations, biopsy of the infected area should be per­formed to confirm the diagnosis of the cause. When drug-related ANCA vasculitis is confirmed, the delivery of medicine must be suspended immediately to avoid further lethal damage.