Any of the available on‐demand therapies for HAE (plasma‐derived C1‐INH concentrate, recombinant C1‐INH concentrate, the kallikrein inhibitor ecallantide and the bradykinin B2 receptor antagonist icatibant) can be used to treat breakthrough attacks in patients using C1‐INH(SC). The gene discussed is KLK4; the disease is hereditary angioedema.