However, the clinical presentation of HAE-C1INH can be similar to other conditions of angioedema without urticaria, including HAE with normal C1INH, acquired angioedema due to C1INH deficiency, acquired angiotensin-converting enzyme inhibitor–associated angioedema, and nonhistaminergic idiopathic angioedema; allergic and idiopathic histamine-mediated angioedema may sometimes also present with angioedema but without urticaria.9 This evidence concerns the gene SERPING1 and hereditary angioedema.