Department of Internal Medicine, Tottori Red Cross Hospital, Tottori, Japan.
Department of Cardiology, Tottori Red Cross Hospital, Tottori, Japan.
Am J Case Rep. 2023 Sep 27;24:e941306. doi: 10.12659/AJCR.941306.
BACKGROUND Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a form of vasculitis predominantly affecting small blood vessels and systemic organs, including the lungs and kidneys. The serum ANCA is an important diagnostic marker for AAV. However, ANCA levels can be nonspecifically elevated in autoimmune diseases like rheumatoid arthritis (RA) and some infectious diseases. Furthermore, RA and AAV can occur together. Therefore, when ANCA is detected in patients with RA, interpretation of the results is often difficult. CASE REPORT A 71-year-old woman with a 15-year history of RA was admitted to our hospital with a fever and anorexia. She was treated with prednisolone 5 mg/day and iguratimod 50 mg/day for the RA. She presented with bilateral frosted glass shadows in the lungs, acute kidney injury, positive myeloperoxidase (MPO)-ANCA results, and elevated ß-D-glucan levels, suggesting AAV or pneumocystis pneumonia. A renal biopsy and bronchoalveolar lavage ruled out AAV. A polymerase chain reaction of the bronchoalveolar lavage fluid was positive for Pneumocystis jirovecii DNA, leading to a diagnosis of pneumocystis pneumonia. After admission, the patient continued to receive intravenous supplemental fluids, and renal function improved. Based on her pathological test results and clinical course, acute kidney injury was diagnosed as prerenal failure due to dehydration in the background of chronic kidney disease. CONCLUSIONS Even if MPO-ANCA is positive in patients with RA, it is important to consider the possibility of a false-positive result and perform a thorough and aggressive examination.
抗中性粒细胞胞浆抗体（ANCA）相关性血管炎（AAV）是一种主要影响小血管和全身器官（包括肺和肾脏）的血管炎形式。血清 ANCA 是 AAV 的重要诊断标志物。然而，在类风湿关节炎（RA）等自身免疫性疾病和某些传染病中，ANCA 水平可能会出现非特异性升高。此外，RA 和 AAV 可以同时发生。因此，当 RA 患者检测到 ANCA 时，结果的解释往往很困难。
一名 71 岁女性，患有 15 年 RA 病史，因发热和厌食症入院。她接受了每天 5 毫克泼尼松龙和每天 50 毫克依古曲米治疗 RA。她表现为双肺磨砂玻璃影、急性肾损伤、髓过氧化物酶（MPO）-ANCA 阳性结果和 β-D-葡聚糖水平升高，提示 AAV 或肺孢子菌肺炎。肾活检和支气管肺泡灌洗排除了 AAV。支气管肺泡灌洗液聚合酶链反应检测到卡氏肺孢子虫 DNA 阳性，诊断为肺孢子菌肺炎。入院后，患者继续接受静脉补液，肾功能改善。根据她的病理检查结果和临床过程，急性肾损伤被诊断为慢性肾脏病基础上的脱水引起的肾前性衰竭。
即使 RA 患者的 MPO-ANCA 阳性，也重要的是要考虑假阳性结果的可能性，并进行彻底和积极的检查。
