Department of Pediatrics, Wakayama Medical University, Wakayama City, Wakayama, Japan.
Department of Pediatrics, Child Health and Welfare (Pediatrics), Graduate School of Medicine, University of the Ryukyus, 207 Uehara Nishihara-cho, Nakagami-gun, Okinawa, 903-0125, Japan.
Pediatr Nephrol. 2021 Apr;36(4):899-908. doi: 10.1007/s00467-020-04772-4. Epub 2020 Oct 4.
IgA nephropathy (IgAN) is characterized by predominant mesangial IgA deposition. Some patients with IgAN demonstrate IgA deposition in glomerular peripheral capillaries (cap-IgA). The clinicopathological significance of cap-IgA remains incompletely investigated in children.
We retrospectively analyzed 503 consecutive cases of biopsy-proven childhood IgAN between July 1976 and June 2013 to compare clinical and pathological features between IgAN patients with and without cap-IgA.
Among the 503 patients, 30 (6.0%) had cap-IgA. We found significant differences in proteinuria (2.0 vs. 0.5 g/day/m, p < 0.0001), time from onset to kidney biopsy (2.2 vs. 8.3 months, p < 0.0001), and rate of proteinuria remission after treatment (23.3% vs. 48.0%, p = 0.007) between both groups. Pathological analysis revealed significant differences in M1 (83.3% vs. 56.0%, p = 0.002), ratio of subendothelial electron dense deposits (EDDs, 58.6% vs. 16.5%, p < 0.0001) and subepithelial EDDs (48.3% vs. 16.5%, p = 0.0001), and glomerular basement membrane (GBM) lysis (58.6% vs. 27.1%, p = 0.0006) between both groups. More than half of cap-IgA patients (17/30, 56.7%), whereas only 26.2% of non-cap-IgA patients (124/473), were treated with immunosuppressive treatments. Six of 30 cases (20%) with cap-IgA reached glomerular filtration rate (GFR) categories G3a-G5 (estimated GFR < 60 ml/min/1.73 m) at most recent observation (mean observation period: 7.0 ± 4.0 years). According to Kaplan-Meier analysis, patients with cap-IgA had significantly lower kidney survival curves than non-cap-IgA patients (72.8% vs. 97.2% at 10 years, p < 0.0001).
Cap-IgA is associated with acute inflammation with GBM changes, resulting in refractory heavier proteinuria. Cap-IgA may represent a poor prognostic factor.
IgA 肾病（IgAN）的特征是主要的系膜 IgA 沉积。一些 IgAN 患者表现为肾小球外周毛细血管（cap-IgA）中的 IgA 沉积。cap-IgA 在儿童中的临床病理意义尚不完全清楚。
我们回顾性分析了 1976 年 7 月至 2013 年 6 月间经活检证实的 503 例连续儿童 IgAN 病例，比较了有和无 cap-IgA 的 IgAN 患者的临床和病理特征。
在 503 例患者中，有 30 例（6.0%）有 cap-IgA。我们发现两组之间蛋白尿（2.0 与 0.5 g/天/m，p < 0.0001）、从发病到肾活检的时间（2.2 与 8.3 个月，p < 0.0001）和治疗后蛋白尿缓解率（23.3%与 48.0%，p = 0.007）存在显著差异。病理分析显示 M1（83.3%与 56.0%，p = 0.002）、内皮下电子致密沉积物（EDD）比例（58.6%与 16.5%，p < 0.0001）和上皮下 EDD（48.3%与 16.5%，p = 0.0001）以及肾小球基底膜（GBM）溶解（58.6%与 27.1%，p = 0.0006）存在显著差异。超过一半的 cap-IgA 患者（17/30，56.7%），而只有 26.2%的非 cap-IgA 患者（124/473）接受了免疫抑制治疗。30 例 cap-IgA 患者中有 6 例（20%）在最近一次观察时达到肾小球滤过率（GFR）类别 G3a-G5（估计 GFR < 60 ml/min/1.73 m）。根据 Kaplan-Meier 分析，有 cap-IgA 的患者的肾脏存活率曲线明显低于无 cap-IgA 的患者（10 年时为 72.8%与 97.2%，p < 0.0001）。
cap-IgA 与 GBM 改变引起的急性炎症有关，导致难治性蛋白尿加重。cap-IgA 可能代表预后不良的因素。
