Pathogenesis of Hereditary Angioedema: The Role of the Bradykinin-Forming Cascade.

Hereditary angioedema (HAE) is an autosomal-dominant disorder owing to mutations in the C1 inhibitor gene. Type I is characterized by a low C1 inhibitor protein level and diminished functional activity, whereas type II has a normal (or elevated) protein level but diminished function. When functional levels drop beyond 40% of normal, attacks of swelling are likely to occur due to overproduction of bradykinin. Angioedema can be peripheral, abdominal, or laryngeal. The typical duration of episodes is 3 days. Therapies include C1 inhibitor replacement for prophylaxis or acute therapy, whereas inhibition of kallikrein or blockade at the bradykinin receptor level can interrupt acute episodes of swelling.