Hereditary angioedema due to C1-INH deficiency (C1-INH-HAE): This is the most common form of HAE and results from a quantitative (Type 1, approximately 85% of patients) or functional (Type 2, approx. 15%) deficiency of C1-INH, the main plasma serine-protease inhibitor of the BK-forming system. This evidence concerns the gene SERPING1 and hereditary angioedema.