Acquired angioedema is a rare disorder characterized by recurrent swelling episodes that can occur anywhere on the body, although the lips and the skin around the eyes are the most frequently affected.
The prevalence of this type of angioedema is difficult to estimate due to its rarity and potential lack of a proper diagnosis. However, some studies estimate that acquired angioedema affects between 1 in 100,000 and 1 in 500,000 people worldwide.
Acquired angioedema occurs when the levels of a protein called C1-inhibitor (C1-INH) are too low. This protein blocks the activity of other proteins, including plasma kallikrein and coagulation factor 12, which are important for blood clotting, inflammation, and wound healing.
As a part of their normal function, these proteins also increase the production of bradykinin, which causes blood vessels in the deep layers of the skin to widen and let fluid flow into tissues, causing swelling. When there isn’t enough C1-INH protein available, bradykinin levels can get too high and cause an angioedema attack.
Levels of the C1-INH protein can be too low for one of two reasons. As such, acquired angioedema can be classed as either type 1 or type 2 according to its cause.
In type 1, the normal function of the immune system is disrupted, resulting in the production of molecules that affect the production or cause the destruction of C1-INH in the body. This disruption can be due to a B-cell lymphoproliferative disorder or an autoimmune disease. In type 1 acquired angioedema, swellings can occur several years before symptoms of other underlying illnesses, making the cause difficult to determine.
Type 2 is an autoimmune disease, in which the body develops self-reactive antibodies that specifically target and destroy its own C1-INH proteins.
Acquired angioedema is a form of angioedema in which swellings take the form of large, smooth welts. These welts are restricted to the lower layers of the skin and mucous membranes, are not itchy, and disappear on their own generally within two to three days. Severe swelling in the intestines or digestive system can cause nausea, vomiting, and intense abdominal pain.
When severe swellings occur in tongue and the mucous membranes of the throat and mouth, they can block the airways and make it difficult to breathe. This can quickly and unexpectedly turn into a life-threatening situation that requires immediate medical attention and emergency treatment. Asphyxiation due to a blocked airway is the most severe complication of acquired angioedema.
Unlike other types of angioedema, symptoms of acquired angioedema usually appear in adults of middle age (onset around age 40 and older).
People with acquired angioedema are considered to be at a higher risk of certain types of cancer, such as B-cell lymphoma (a type of blood cancer), than is the general population.
Acquired angioedema typically does not respond to standard treatments for other forms of angioedema, such as corticosteroids, antihistamines, or epinephrine.
In life-threatening situations where swelling in the throat or mouth has blocked the airway and an individual is having trouble breathing, hospital admission could be required for swift and proper treatment.
Medicines that boost C1-INH levels in the body are generally effective for treating acquired angioedema. For example, Berinert, a plasma-derived C1-INH concentrate, has been reported to treat both type 1 and type 2 acquired angioedema.
Kalbitor (ecallantide) was also found to be a promising option in the treatment of patients who do not respond to C1-INH concentrates. Firazyr (icatibant) can be used for immediate relief of attack symptoms.
As these medicines may not be available in an emergency, fresh frozen plasma may also be used.
Treating the underlying cause of the disorder — an immune system-affecting disease in type 1 or autoimmune activity in type 2 — can also help ease symptoms of acquired angioedema.
Last updated: Dec. 28, 2021, by Teresa Carvalho MSc
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