If C4 antigenic protein and C1-INH functional assays are both normal, this rules out Types I and II HAE but does not rule out type III HAE (HAE-FXII and HAE-Unknown) (normal C1-INH protein and function occurring mainly in women; some with mutations in the coagulation factor XII gene or other unidentified defects; [11,13,19,25,35] nor medication-related angioedema (e.g. ACE-I-related Angioedema; [10,19,22]). Here, C4A is linked to angioedema.