All patients had a previous diagnosis of recurrent angioedema due to C1INH deficiency (29 patients with HAE-C1INH and 1 patient with acquired angioedema due to C1INH deficiency, established by biochemical testing [antigenic C4 and/or antigenic C1INH and/or fC1INH] and family history, with genetic tests for SERPING1 obtained in case of any ambiguity) as a part of their regular care before and unrelated with the sample collection for this study. Here, C4A is linked to acquired angioedema.