This guideline aims to describe the complement system and the functions of the constituent pathways, with particular focus on primary immunodeficiencies (PIDs) and their diagnosis and management. The complement system is a crucial part of the innate immune system, with multiple membrane-bound and soluble components. There are three distinct enzymatic cascade pathways within the complement system, the classical, alternative and lectin pathways, which converge with the cleavage of central C3. Complement deficiencies account for ~5% of PIDs. The clinical consequences of inherited defects in the complement system are protean and include increased susceptibility to infection, autoimmune diseases (e.g., systemic lupus erythematosus), age-related macular degeneration, renal disorders (e.g., atypical hemolytic uremic syndrome) and angioedema. Modern complement analysis allows an in-depth insight into the functional and molecular basis of nearly all complement deficiencies. However, therapeutic options remain relatively limited for the majority of complement deficiencies with the exception of hereditary angioedema and inhibition of an overactivated complement system in regulation defects. Current management strategies for complement disorders associated with infection include education, family testing, vaccinations, antibiotics and emergency planning.

中文翻译：

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欧洲免疫缺陷协会 (ESID) 和欧洲罕见原发性免疫缺陷、自身炎症和自身免疫性疾病参考网络 (ERN RITA) 补充指南：缺陷、诊断和管理。

本指南旨在描述补体系统及其组成途径的功能，特别关注原发性免疫缺陷（PID）及其诊断和治疗。补体系统是先天免疫系统的重要组成部分，具有多种膜结合和可溶性成分。补体系统内存在三种不同的酶级联途径，即经典途径、替代途径和凝集素途径，它们与中央 C3 的裂解汇合。补体缺陷约占 PID 的 5%。补体系统遗传性缺陷的临床后果多种多样，包括感染易感性增加、自身免疫性疾病（例如系统性红斑狼疮）、年龄相关性黄斑变性、肾脏疾病（例如非典型溶血性尿毒症综合征）和血管性水肿。现代补体分析可以深入了解几乎所有补体缺陷的功能和分子基础。然而，除了遗传性血管性水肿和抑制调节缺陷中过度激活的补体系统外，大多数补体缺陷的治疗选择仍然相对有限。目前针对与感染相关的补体疾病的管理策略包括教育、家庭检测、疫苗接种、抗生素和应急计划。