Types of Angioedema
Angioedema can be characterized as :
This is an immune reaction to an allergen. Symptoms may appear within the first 2 hours after exposure to the allergen and usually settle within 3 days. Urticaria is usually present but not always.
This type of angioedema is associated with certain types of autoimmune diseases, infections, malignant tumors and diseases causing increased lymphocyte populations. It tends to occur later in life, usually after the fourth decade, and may persist as long as the underlying disease is present (chronic in nature). Urticaria may be present.
This is inherited type of angioedema and the symptoms usually present before the age of 20 years. It typically occurs in episodes, which can be quite severe and affect multiple systems simultaneously.
Drug Induced Angioedema
This is a non-allergenic type of angioedema and occurs within days or weeks (sometimes longer) after starting a certain type of medication. Urticaria is not present.
Symptoms are similar to acute allergic angioedema.
Causes of Angioedema
Each type of angioedema has key features and causes which differentiates it from other types.
Acute Allergic Angioedema
In this type of angioedema, the presence of an allergen (list below) triggers the release of histamine from mast cells (an immune cell).
- Food allergies (example dairy, wheat, soy, nuts, shellfish, eggs – particularly the egg yolk) and insect bites (example bee stings, spider bites) are the most common cause.
- Pharmaceutical drugs like penicillin, certain NSAID’s.
- Latex and certain artificial fibers.
- Animal dander (fur, hair, feathers).
These are the most common, but not the only, allergens that may cause acute allergic angioedema.
In this type of angioedema, the control mechanism of the immune chemical, C1, is targeted and destroyed by the immune system. This allows the immune chemical to remain activated and trigger other immune related processes which increases vascular permeability. This control mechanism is the chemical C1-INH (C1 esterase inhibitor) and autobodies against it are present.
The exact cause for the development of these C1-INH autoantibodies have not been conclusively identified. However, it is found that it does occur when certain autoimmune disorders, infections, cancers and immune cells diseases are existing. Some of these conditions include :
- Systemic lupus erythematosus.
- Multiple myeloma.
- Non-Hodgkin’s lymphoma.
- Chronic Helicobacter pylori infection.
- Chronic lymphocytic leukemia.
As in acquired angioedema, C1-INH is in low quantities. There is a familial link to this type of angioedema and the synthesis of C1-INH is disrupted due to an abnormal gene. Essentially there is a C1-INH deficiency.
While the cause is genetic in nature, there may be some precipitating factors that can trigger angioedema attacks. All of these triggers have not as yet been identified but in some cases it may be due to increased levels of estrogen during pregnancy.
Drug Induced Angioedema
Certain types of drugs may trigger the activation and release of certain types of vasoactive substances. These substances increases the vascular permeability thereby resulting in angioedema.
ACE-inhibitors, a drug commonly used for hypertension, is known to cause this type of angioedema in susceptible patients.
As the name suggests, the cause of this type of angioedema is unknown