Acute treatment of HAE includes intravenous infusions of plasma-derived C1-INH (pdC1-INH), recombinant human C1-INH (rhC1-INH), icatibant (bradykinin B2-receptor antagonist), or ecallantide (recombinant plasma kallikrein inhibitor). This evidence concerns the gene KLK4 and hereditary angioedema.