Hereditary angioedema (HAE) is an autosomal dominant disease resulting from the deficiency of C1 inhibitor (C1-INH), a glycosylated serine protease inhibitor that plays a regulatory role in the complement system (CS), the contact system and the intrinsic coagulation cascade. HAE disease severity is highly variable and may be influenced by genetic polymorphisms as well as by other factors, such as gender hormone-mediated effects. In HAE, the potential inadequate clearance of immune-complexes (IC) in the presence of reduced levels of CS components and in turn an excess of IC in the tissues results in inflammatory damage and release of autoantigens that may trigger an autoimmune response. Occasional reports link HAE with autoimmune conditions and only few studies have been conducted on large patient populations with controversial results. Although several immunoregulatory disorders have been documented, the prevalence of defined autoimmune diseases in patients with HAE remains debated. The occurrence of autoimmune conditions in HAE patients may worsen the disease severity enhancing the complexity of the comprehensive care. (C) 2015 Elsevier B.V. All rights reserved.