Classification
Angioedema is classified as either hereditary or acquired.
Acquired angioedema can be immunologic, nonimmunologic, or idiopathic. It is usually caused by allergy and occurs together with other allergic symptoms and urticaria. It can also occur as a side effect to certain medications, particularly ACE inhibitors.
Hereditary angioedema (HAE) exists in three forms, all of which are caused by a genetic mutation inherited in an autosomal dominant form. They are distinguished by the underlying genetic abnormality. Types I and II are caused by mutations in the SERPING1 gene, which result in either dimished levels of the C1-inhibitor protein (type I HAE) or dysfunctional forms of the same protein (type II HAE). Type III HAE has been linked with mutations in the F12 gene, which encodes the coagulation protein factor XII. All forms of HAE lead to abnormal activation of the complement system, and all forms can cause swelling elsewhere in the body, such as the digestive tract. If HAE involves the larynx, it can cause life-threatening asphyxiation. The pathogenesis of this disorder is suspected to be related to unopposed activation of the contact pathway by the initial generation of kallikrein and/or clotting factor XII by damaged endothelial cells. The end product of this cascade, bradykinin, is produced in large amounts and is believed to be the predominant mediator leading to increased vascular permeability and vasodilation that induces typical angioedema "attacks".
Read more about this topic: Angioedema