Autoantibodies and deposition of immune complexes into tissues have been clearly linked to the pathogenesis of several of the ADs identified in this systematic review as most commonly co-occurring with HAE-C1INH, including SLE, GN, thyroid disease, RA, and Sjogren’s syndrome [18, 43–46]. This evidence concerns the gene SERPING1 and systemic lupus erythematosus.