Although there is no compelling evidence whether microbial compounds indeed directly trigger angioedema attacks, we previously described a decreased frequency of abdominal attacks in C1-INH-HAE patients following eradication of the stomach mucosal-resident pathogen Helicobacter pylori [235], which suggests that bacterial macromolecules may indeed be permeability modifying trigger-factors either directly, or via the activation of immune and/or neural system. This evidence concerns the gene SERPING1 and angioedema.