Abstract：
Antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) typically manifests as rapidly progressive glomerulonephritis with crescent formation. In this report, we present a local case of myeloperoxidase (MPO)-AAV-associated acute interstitial nephritis (AIN), showing slight pauci-immune glomerulonephritis and positive MPO-ANCA. This case is characterized by foot process effacement of podocytes in the glomerulus, a favorable prognosis, and an absence of crescentic formation. To further understand this condition, we conducted a comprehensive literature search on Google Scholar and PubMed, employing both free text words and MeSH terms related to \"AAV and AIN.\" This search yielded 24 cases, which we analyzed for their clinical features, laboratory findings, renal pathological characteristics, and therapeutic outcomes. AAV-associated interstitial nephritis predominantly affects elderly patients and is often associated with anemia, proteinuria, hematuria, and nonspecific manifestations, including fever, anorexia, fatigue, edema, and weight loss. Most of the cases in our review were MPO-ANCA-positive and exhibited isolated interstitial inflammation. These patients typically presented with relatively lower levels of serum creatinine, 24-h urine protein levels, and MPO-ANCA titers. All patients in our study received immunosuppressive therapy, including glucocorticoids, immunosuppressants, and rituximab, with the majority achieving clinical remission. Isolated AIN in the context of AAV is a rare occurrence, but it displays distinct clinical, laboratory, and pathological features. Patients with this presentation show a positive response to immunosuppressive treatment. Nevertheless, the establishment of definitive therapy guidelines for AAV-associated AIN remains uncertain and necessitates further investigation to develop comprehensive treatment guidelines. AIN, particularly when lacking typical glomerulus lesions, may represent a novel subgroup within MPO-AAV warranting additional research and clinical attention. Key Points • This study contributes valuable scientific insights by highlighting that MPO-AAV-associated interstitial nephritis, even without crescentic formation, can exhibit podocyte foot process effacement and respond well to treatment. • The presence of AIN, independent of crescentic glomerulonephritis, suggests the potential emergence of a new subclass within MPA-AAV. • Notably, some cases of MPO-AAV-associated AIN may present with normal levels of Scr (Table 5, cases 5, 6, and 17). • This observation highlights the importance of considering renal biopsy, diagnosis, and therapy in a timely manner to prevent the development of chronic kidney disease (CKD).
摘要：
抗中性粒细胞胞浆抗体（ANCA）相关血管炎（AAV）通常表现为快速进行性肾小球肾炎，并伴有新月形成。在这份报告中,我们介绍了一个髓过氧化物酶（MPO）-AAV相关急性间质性肾炎（AIN）的局部病例，表现为轻微的隐蔽性肾小球肾炎和MPO-ANCA阳性。这种情况的特征是肾小球足细胞的足突消失，良好的预后，和缺乏新月形成。为了进一步了解这种情况，我们对GoogleScholar和PubMed进行了全面的文献检索，同时使用与“AAV和AIN”相关的自由文本单词和MeSH术语。“这次搜索产生了24个案例，我们分析了它们的临床特征，实验室发现,肾脏病理特征，和治疗结果。AAV相关的间质性肾炎主要影响老年患者，通常与贫血有关。蛋白尿,血尿,和非特异性表现，包括发烧,厌食症,疲劳,水肿,和减肥。我们审查中的大多数病例均为MPO-ANCA阳性，并表现出孤立的间质性炎症。这些患者通常血清肌酐水平相对较低，24小时尿蛋白水平，和MPO-ANCA滴度。我们研究的所有患者都接受了免疫抑制治疗，包括糖皮质激素,免疫抑制剂,利妥昔单抗,大多数患者达到临床缓解。在AAV的背景下，孤立的AIN是罕见的，但它显示出不同的临床，实验室,和病理特征。具有这种表现的患者对免疫抑制治疗表现出积极的反应。然而，AAV相关AIN的最终治疗指南的建立仍不确定,需要进一步研究以制定综合治疗指南.AIN,特别是当缺乏典型的肾小球病变时，可能代表MPO-AAV中的一个新亚组，需要额外的研究和临床关注。要点•这项研究通过强调MPO-AAV相关的间质性肾炎，即使没有新月形成，能表现出足细胞足过程消失，对治疗反应良好。•AIN的存在，独立于新月体肾小球肾炎，提示MPA-AAV中可能出现新的亚类。•值得注意的是，一些MPO-AAV相关AIN病例可能存在Scr水平正常的情况(表5,病例5,6和17).•这一观察结果突出了考虑肾活检的重要性，诊断,并及时治疗，以防止慢性肾脏病（CKD）的发展。
