Department of Pathology, Division of Renal Pathology, Ohio State University Wexner Medical Center, Columbus, OH, USA.
Department of Nephrology, Hospital Fernandez, Buenos Aires, Argentina.
Nephrol Dial Transplant. 2020 Dec 4;35(12):2123-2129. doi: 10.1093/ndt/gfz152.
Primary immunoglobulin A nephropathy (IgAN) is characterized by IgA1-dominant or codominant glomerular deposits, postulated to be galactose deficient (Gd). However, glomerular IgA deposition can also occur in nonrenal diseases such as liver cirrhosis, psoriasis and inflammatory bowel disease ('secondary IgAN') or be an incidental finding in biopsies with other pathologies. A glomerulonephritis resembling IgAN can develop in patients with bacterial, mainly staphylococcal infections [staphylococcal infection-associated glomerulonephritis (SAGN)]. There are no specific histological features to distinguish between these, but differentiation is critical for appropriate management. The aim of this study was to investigate whether a recently described antibody to Gd-IgA1 (KM-55) could aid in differentiating primary IgAN from other conditions with glomerular IgA deposition, especially SAGN.
We performed a retrospective cohort study of patients who underwent kidney biopsy for clinical indications and were found to have glomerular IgA deposits.
We evaluated 100 biopsies, including primary IgAN (n = 44), secondary IgAN (n = 27), SAGN (n = 13), incidental IgA deposition (n = 8) and lupus nephritis (n = 8). There was no difference in Gd-IgA staining intensity or the proportion of positive cases between primary and secondary IgAN. SAGN and cases with incidental IgA deposits had significantly lower Gd-IgA staining intensity than primary IgAN, but up to 69% of SAGN cases were positive (albeit weaker).
Gd-IgA staining is present not only in primary IgAN, but also in biopsies with secondary IgAN, SAGN and incidental IgA. Weak or negative staining may favor SAGN, especially in the setting of infection, or incidental IgA in the absence of nephritic symptoms or in the presence of other unrelated glomerular pathologies. However, positive staining for Gd-IgA alone is not specific enough for a diagnosis of primary IgAN.
原发性免疫球蛋白 A 肾病（IgAN）的特征是 IgA1 占优势或共占优势的肾小球沉积物，推测为半乳糖缺乏（Gd）。然而，肾小球 IgA 沉积也可能发生在非肾脏疾病中，如肝硬化、银屑病和炎症性肠病（“继发性 IgAN”），或在其他病理活检中偶然发现。类似于 IgAN 的肾小球肾炎可发生在细菌感染的患者中，主要是葡萄球菌感染[葡萄球菌感染相关性肾小球肾炎（SAGN）]。没有特定的组织学特征来区分这些，但区分对于适当的管理至关重要。本研究旨在探讨一种最近描述的针对 Gd-IgA1 的抗体（KM-55）是否有助于区分原发性 IgAN 与其他具有肾小球 IgA 沉积的疾病，特别是 SAGN。
我们对因临床指征接受肾活检并发现有肾小球 IgA 沉积的患者进行了回顾性队列研究。
我们评估了 100 例活检，包括原发性 IgAN（n=44）、继发性 IgAN（n=27）、SAGN（n=13）、偶然 IgA 沉积（n=8）和狼疮肾炎（n=8）。原发性和继发性 IgAN 之间 Gd-IgA 染色强度或阳性病例比例无差异。SAGN 和偶然 IgA 沉积的病例 Gd-IgA 染色强度明显低于原发性 IgAN，但高达 69%的 SAGN 病例为阳性（尽管较弱）。
Gd-IgA 染色不仅存在于原发性 IgAN，也存在于继发性 IgAN、SAGN 和偶然 IgA 沉积的活检中。弱阳性或阴性染色可能提示 SAGN，尤其是在感染情况下，或在无肾炎症状或存在其他无关的肾小球病变的情况下偶然存在 IgA。然而，单独 Gd-IgA 染色阳性不足以诊断原发性 IgAN。
