Hereditary angioneurotic edema: A genetic form of angioedema due to C1-inhibitor deficiency (HAE-C1-INH). A rare, autosomal-dominant disease, HAE-C1-INH is characterized by recurrent attacks of marked, diffuse, nonpitting and nonpruritic skin swellings, painful abdominal attacks, and laryngeal edema. The extremities and the gastrointestinal tract are most commonly affected. Swelling of the upper respiratory mucosa poses the greatest risk because death from asphyxiation. Attacks are variable, may be the result of stress or physical trauma. The diagnosis is suspected with a history of recurrent angioedema. It is confirmed by finding abnormally low levels of C1 esterase inhibitor in the blood. Treatment may include a variety of medications and therapy.