The phenotype and pattern of inheritance are the same, but the diagnostic approaches are different: while in HAE-C1INH type 1 it is sufficient to demonstrate an antigenic deficiency of the protein by turbidimetry, nephelometry, radial immunodiffusion, immunoblotting, or other immunologic methods, the diagnosis of HAE-C1INH type 2 requires assessment of functional C1INH activity by chromogenic or ELISAs, which need special attention even at the preanalytical stage (1, 10, 36–39). The gene discussed is SERPING1; the disease is hereditary angioedema.