Angioedema is characterized by a well-demarcated swelling on the skin, oropharyngolaryngeal tissue, or the gastrointestinal wall. Underlying mechanisms may include IgE-mediated reactions, complement activation, inhibition of the cyclo-oxygenase pathway of arachidonic acid metabolism, direct release of mediators from mast cells, and activation of the kinin-forming system. Foods, drugs, inhalants, insect bites, blood transfusion, collagen vascular disease, infections, physical factors, neoplasms, and hereditary factors can cause angioedema through one or more of these mechanisms. Chronic angioedema lasts more than 6 weeks or recurs during this period. Acute angioedema is a self-limited disorder and resolves spontaneously, or with simple therapy, in several days; the patient rarely requires a complete work-up. Chronic angioedema may necessitate a detailed history, physical examination, and limited clinical or laboratory tests to exclude serious underlying illnesses. The H1 antihistamines are used for the treatment of both acute and chronic angioedema. An H2 antihistamine, a second H1 antihistamine, or rarely even a low dose of corticosteroid may be added to the regimen if H1 antihistamine alone fails to control chronic angioedema. Hereditary angioedema is an autosomal dominant disease that is caused by C1INH deficiency. In patients with this disorder, swelling of the lip, pharynx, and extremities may follow trauma to soft tissue. Other clinical manifestations include abdominal pain, nausea, vomiting, and suffocation because of laryngeal swelling. Diagnosis can be confirmed by the finding of low levels of C4 and C2 and the absence of nonfunction of C1INH. Androgens reverse the biochemical defects.

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