SERPING1 and hereditary angioedema: Reasons include (1) that no mutation of the C1-INH gene can be detected in 8% to 10% of cases, (2) that identical mutations may be associated with substantially different phenotypes, (3) that C1-INH mutations may cause a nonfatal manageable disease in the offspring, the severity of which cannot be predicted in advance, and (4) recent advances in therapy have significantly improved quality of life of patients with HAE [116,118,119].