,24 Diagnosis of HAE Type II is particularly impeded by a lack of fC1INH testing, even when other diagnostic tests for HAE (antigenic C4 and/or antigenic C1INH testing) are available, because antigenic C1INH and antigenic C4 testing may fail to correctly identify patients with HAE Type II.24 The gene discussed is C4A; the disease is hereditary angioedema.