C4A and angioedema: The most common criteria used to diagnose HAE-nC1INH included the assessment of a positive family history of angioedema (90%), normal plasma C4 levels (90%), normal C1INH functional and quantitative (antigenic) levels (each 87%), mutations in factor XII (83%), lack of response to antihistamines (73%), response to HAE-specific medications (70%), and mutations in plasminogen (67%) (Fig 3, C).