Methods: Two cohorts of participants 18 and older were recruited from the United States Hereditary Angioedema Association (US HAEA) with a documented history of HAE due to C1-inhibitor deficiency (HAE-C1-INH): Cohort 1, self-referred; Cohort 2, randomized from the HAEA membership roster. This evidence concerns the gene SERPING1 and C1 inhibitor deficiency.