SERPING1 and hereditary angioedema: Although pathogenic variations in SERPING1 are the only known cause of the development of HAE types I and II, there are reported 5−10% symptomatic HAE patients with reduced C1-INH levels and/or functional activity in whom pathogenic variations cannot be found, even after carrying out a thorough genetic examination (including the entire SERPING1 gene sequencing of the coding and non-coding parts of the gene and analysis of copy number variants) [39, 40].