I. Idiopathic |
II. Medications (allergic or non-allergic)  ACE inhibitors: activated bradykinin ↑  NSAIDs: COX 1 inhibition → leukotrienes ↑ |
III. Allergen-induced (foods, etc.): histamine ↑ (IgE mediated) |
IV. Physically induced (cold, pressure, vibration, ultraviolet, etc.): histamine ↑ (direct) |
V. Deficiency or inactivation of C1-INH : uncontrolled complement activation → bradykinin ↑  1. HAE   a. HAE type 1 (80–85 %): decreased level of C1-INH   b. HAE type 2 (10–15 %): normal or high levels of dysfunctional C1-NIH  2. AAE with C1-INH deficiency   a. AAE type 1 associated mainly with lymphoproliferative disorders (e.g., lymphoma)   b. AAE type 2 associated with anti-C1-INH autoantibodies (e.g., autoimmune diseases) |
VI. HAE type 3 (rare): normal or slightly low C1-INH level with normal function  1. Coagulation factor XII gene mutation (HAE-FXII): activated factor XII ↑ → bradykinin ↑  2. HAE-unknown |