Hereditary and acquired angioedema

[Dorothey Allen]

Hereditary angioedema (a genetic disorder) and acquired angioedema (acquired C1 inhibitor deficiency) are caused by a deficiency or malfunction of C1 inhibitor, which is part of the immune system. Both disorders result in repeated episodes of swelling under the skin.
(See also Overview of Allergic Reactions.)
Hereditary angioedema and acquired angioedema resemble angioedema caused by an allergic reaction, with swelling of areas of tissues under the skin. However, hives do not develop, and the cause is different.
Hereditary angioedema is a genetic disorder that causes a deficiency or malfunction of C1 inhibitor. C1 inhibitor is one of the proteins in the complement system, which is part of the immune system. Symptoms usually start during childhood or adolescence.
Acquired angioedema, a rare disorder, differs from hereditary angioedema. It develops when certain cancers, such as lymphoma, or autoimmune disorders, such as systemic lupus erythematosus (lupus) or dermatomyositis, cause a deficiency of C1 inhibitor. Symptoms usually start later in life, after people have developed a disorder that can cause this deficiency.
In both hereditary and acquired angioedema, swelling (angioedema) may be triggered by

A minor injury, as may occur during a dental procedure
A viral infection
Certain foods
Pregnancy
Exposure to cold

Stress, such as that due to anticipating or having a dental or surgical procedure, can make angioedema worse.