Atypical hemolytic uremic syndrome (aHUS) is caused mainly by complement dysregulation. Although various defects in the complement system explaining pathophysiology have been described in recent years, the etiology still remains unclear in about thirty percent of cases. In exploring other causes, similar to anti- complement factor H (anti-CFH) antibody associated HUS, we hypothesized that anti-complement factor I (anti-CFI) antibody could play a role in aHUS. Further, we tried to describe the clinical profile and outcome of those with high anti CFI antibody titers. Eleven of thirty five children (31 %) diagnosed with aHUS from July 2017 to December 2018 had high IgG anti-CFI antibody titers. Median age was 10 months (6, 33) with no sex difference. Thirty-six percent (4/11) had nephrotic-range proteinuria. C3 was low in 8 children (72.7 %) with mean C3 (68.1 ± 14.7 mg/dL). Plasmapheresis was done in 2 children who promptly responded, suggesting the possible role of anti-CFI antibody in pathogenesis of aHUS in these patients. Further studies examining role of anti-CFI antibodies in aHUS is warranted with longitudinal and genetic studies.

非典型溶血性尿毒症综合征 (aHUS) 主要由补体失调引起。尽管近年来已经描述了解释病理生理学的补体系统中的各种缺陷，但在大约 30% 的病例中病因仍然不清楚。在探索其他原因时，类似于抗补体因子 H（抗 CFH）抗体相关的 HUS，我们假设抗补体因子 I（抗 CFI）抗体可能在 aHUS 中起作用。此外，我们试图描述那些具有高抗 CFI 抗体滴度的临床特征和结果。2017 年 7 月至 2018 年 12 月诊断为 aHUS 的 35 名儿童中有 11 名 (31%) 具有高 IgG 抗 CFI 抗体滴度。中位年龄为 10 个月 (6, 33)，无性别差异。百分之三十六 (4/11) 有肾病范围的蛋白尿。8 名儿童 (72. 7 %)，平均 C3 (68.1 ± 14.7 mg/dL)。对 2 名迅速反应的儿童进行了血浆置换，表明抗 CFI 抗体可能在这些患者的 aHUS 发病机制中发挥作用。进一步研究检查抗 CFI 抗体在 aHUS 中的作用需要纵向和遗传研究。