Angioedema is characterized by episodes of severe swelling. The swelling mostly occurs on the face and limbs, but may also affect other areas, like the intestinal tract and airways.
Angioedema can have several causes, including allergies, reactions to medications, and genetic factors. There are different types of angioedema based on its underlying cause or causes.
Acute allergic angioedema
Acute allergic angioedema is the most common type, and a consequence of an allergic reaction. In this type of angioedema, the body mistakenly identifies certain external substances, such as food or medications, as harmful. It then launches an immune attack against these substances. As part of the immune attack, immune cells produce signaling molecules that promote swelling, ultimately triggering the condition.
Non-allergic angioedema, also called drug-induced angioedema, is a side effect of specific medications like angiotensin-converting enzyme (ACE) inhibitors. The onset of this type of angioedema may vary from days to months after exposure to the medication.
Idiopathic angioedema is the name given to angioedema that has no clear cause. It is often chronic, relapsing, and mostly accompanied by hives or welts.
Hereditary angioedema (HAE) is a form of angioedema caused by genetic mutations. These mutations are usually inherited from a person’s biological parents; as such, most people with HAE have a family history of the disease. About 20-25% of HAE cases occur due to spontaneous mutations (i.e., in people who do not have a family history of the condition).
Hereditary angioedema can be divided into three types, depending on the specific mutations involved.
HAE type 1
This is the most common type of HAE, accounting for more than 80% of HAE cases.
This particular type is caused by mutations in the SERPING1 gene, which encodes the C1 inhibitor (C1-INH) protein. This protein normally blocks the activity of other proteins that promote swelling. In this type of HAE, mutations in SERPING1 lower the production of C1-INH.
HAE type 2
Type 2 HAE accounts for approximately 15–20% of HAE cases.
Like type 1, type 2 HAE is caused by mutations in the SERPING1 gene. However, whereas type 1 severely lowers C1-INH levels, in type 2 a normal amount of protein is made, but the produced protein does not work as it should.
HAE type 3
This type of HAE is very rare. It is caused by mutations in the F12 gene, which is responsible for the production of a protein called coagulation factor 12. Mutations in this gene result in the production of overactive coagulation factor 12. This, in turn, leads to higher production of bradykinin, a molecule that promotes inflammation and swelling. Although predominant in females, this type of hereditary angioedema can affect people of all sexes.
Like type 1 HAE, acquired angioedema is caused by abnormally low levels of the C1-INH protein; however, its low protein levels are not the result of genetic mutations. Often, acquired angioedema is caused by the body’s immune system erroneously creating antibodies that destroy the C1-INH protein. Some infections and cancers may also cause C1-INH levels to drop.
Last updated: July 2, 2021
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