,11 Furthermore, diagnosis of acquired angioedema due to C1INH deficiency may need to be excluded in patients with negative family history and symptom onset after the age of 30 years; antigenic C4, antigenic C1INH, and functional C1INH (fC1INH) findings of this condition are consistent with HAE Type I.3fC1INH is markedly reduced in both HAE Type I and HAE Type II; therefore, its measurement is important for diagnosis of HAE-C1INH as the most straightforward assessment.3 This evidence concerns the gene C4A and hereditary angioedema.