immunology allergic disorders
Angioedema
Acute angioedema
Acute angioedema is mast cell–mediated in > 90% of cases. Mast cell–mediated mechanisms include acute allergic, typically IgE-mediated reactions. IgE-mediated angioedema is usually accompanied by acute Urticaria (local wheals and erythema in the skin) and itching. It may often be caused by the same allergens (eg, drug, venom, dietary, extracted allergens) that are responsible for acute IgE-mediated urticaria. Acute angioedema can also result from agents that directly stimulate mast cells without involving IgE. Causes can include opiates, radiopaque contrast agents,aspirin, and nonsteroidal anti-inflammatory drugs (NSAIDs). Angiotensin-converting enzyme (ACE) inhibitors cause up to 30% of cases of acute angioedema seen in emergency departments. ACE inhibitors can directly increase levels of bradykinin. The face and upper airways are most commonly affected, but the intestine may be affected. Urticaria does not occur. Angioedema may occur soon or years after therapy begins. 