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Nancy Romero Reyes.
Angioedema
Author: Allysia M Guy, MD, Staff Physician, Department of Emergency Medicine, State University of New York Downstate Medical Center, Brooklyn, New York
Coauthor(s): Richard H Sinert, DO, Associate Professor of Emergency Medicine, Clinical Assistant Professor of Medicine, Research Director, State University of New York College of Medicine; Consulting Staff,Department of Emergency Medicine, Kings County Hospital Center
Contributor Information and Disclosures
Updated: Aug 12, 2010
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Introduction
Background
Many types of angioedema are described in the literature: hereditary angioedema (HAE) types I, II, and III; acquired angioedema; drug-inducedangioedema (associated with angiotensin-converting enzyme [ACE] inhibitors and angiotensin II receptor blockers [ARBs]); urticaria-associated angioedema; and idiopathic angioedema.1 Most forms of angioedema are considered idiopathic. In general, angioedema can be categorized as with urticaria or without urticaria. Urticaria and angioedema are similar in pathogenesis; however, angioedema manifests deeperin mucosal tissue. The reaction is mast cell mediated when both are evident during clinical presentation.2 In this case, the patient describes subjective pruritus, often associated with hypersensitivity to an offending agent.

Ten percent of angioedema cases occur without urticaria and is considered to be kinin-mediated rather than a hypersensitivity reaction.3 Hereditary angioedema andacquired angioedema are associated with insufficient or dysfunctional C1 esterase inhibitor, resulting in increased circulation of vasoactive substances. This type of angioedema can be induced spontaneously, or it can be due to stress or medications; this type is highly associated with ACE inhibitors.

In general, angioedema is described as deep, subcutaneous, submucosal edema due to increased vascularpermeability. It can manifest as an episodic or self-limiting event but can often be described as recurrent. Acute episodes may involve the skin, larynx, and buccal and gastrointestinal (GI) mucosa.
Pathophysiology
Angioedema without urticaria can be classified as hereditary angioedema (HAE) or acquired C1 inhibitory deficiency (AAE/ACID). Hereditary angioedema results from a quantitative orqualitative deficiency of the C1 esterase inhibitor (C1-INH) due to a defective C1NH gene. Type I is described as C1 esterase inhibitor deficiency. Type II is believed to be a dysfunction of C1 esterase inhibitor with normal-to-high circulating levels of the molecule. These two forms are not distinguishable clinically.

An additional type III HAE, occurring only in females, has also beendescribed. In this case, there is also an abnormal functioning protein. Abdominal attacks are seen less frequently in this variant. Orofacial involvement seems to be the most common presentation of the type III sensitivity, making it very difficult to distinguish from types I and II. This type has also been associated with exogenous estrogen administration and pregnancy.

C1 esterase is a serine proteasethat is involved in the regulation of bradykinin, a potent vasoactive substance. Low levels of this protease results in the activation of the kallikrein-kinin system, the complement cascade, and the fibrinolytic system and results in the release of vasoactive peptides such as bradykinin, considered to be the most important regulatory complement involved in many molecular cascades.6,1 Release ofvasoactive substances causes vasodilatation of endothelial cells as well as smooth muscle bowel contraction.7 This ultimately manifests in the common clinical presentation of the disease.

In the setting of hereditary angioedema, AAE, and ACE inhibitor – induced angioedema, bradykinin levels are directly elevated in the blood.2 ACE is naturally one of the inhibitors of bradykinin. With ACE...
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