Hereditary angioedema (a genetic disorder) and acquired angioedema (also called 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.
Angioedema is swelling of areas of tissue under the skin that sometimes affects the face, throat, and airways.
Most angioedema is caused by an allergic reaction, but sometimes it is caused by a hereditary disorder or another disorder such as cancer.
Unlike angioedema caused by an allergic reaction, hereditary angioedema and acquired angioedema do not cause hives or itching.
Blood tests help doctors diagnose the disorder.
Certain medications can help relieve symptoms, but if angioedema makes swallowing or breathing difficult, prompt emergency treatment is needed.
(See also Overview of Allergic Reactions.)
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
Medications that contain or are related to estrogen
Certain medications for high blood pressure such as angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs)
Exposure to cold
Although certain foods and medications may trigger the angioedema, it is not an allergic reaction to those substances.
Stress, such as that felt before having a dental or surgical procedure, can make angioedema worse.
Symptoms of Hereditary and Acquired C1 Inhibitor Deficiency
The face, lips, tongue, the back of the hands or feet, genitals, and/or other areas of the body may swell. Typically, the swollen areas are slightly painful and not itchy. Hives do not appear. Swelling usually resolves in 1 to 3 days.
The membranes lining the mouth, throat, and airways may also swell. People may make a gasping sound when they breathe in. Such swelling can interfere with breathing and be life threatening. If these symptoms develop, people should see a doctor right away.
The membranes lining the digestive tract may also swell. Nausea, vomiting, and cramps are common.
This photo shows swelling of the lips in a person with hereditary angioedema.
By permission of the publisher. From Joe E, Soter N. In Current Dermatologic Diagnosis and Treatment, edited by I Freedberg, IM Freedberg, and MR Sanchez. Philadelphia, Current Medicine, 2001.
This person has a swollen tongue due to angioedema.
SCIENCE PHOTO LIBRARY
This person has swollen lips due to angioedema.
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
This photo shows swelling of the lips in a person with hereditary angioedema.
By permission of the publisher. From Joe E, Soter N. In Current Dermatologic Diagnosis and Treatment, edited by I Freedberg, IM Freedberg, and MR Sanchez. Philadelphia, Current Medicine, 2001.
This person has a swollen tongue due to angioedema.
SCIENCE PHOTO LIBRARY
This person has swollen lips due to angioedema.
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
Diagnosis of Hereditary and Acquired C1 Inhibitor Deficiency
Blood tests
Doctors suspect hereditary or acquired angioedema if both of the following are present:
People have swelling in the face, lips, tongue, hands, feet, genitals, and/or other areas of the body but do not have hives.
The swelling recurs, and no cause is apparent.
Doctors also suspect one of these disorders if angioedema is triggered by a minor injury.
If family members also have these symptoms, doctors suspect hereditary angioedema.
Doctors diagnose hereditary or acquired C1 inhibitor deficiency by measuring C1 inhibitor levels or activity in a sample of blood.
Treatment of Hereditary and Acquired C1 Inhibitor Deficiency
Fresh frozen plasma
Medications to prevent future attacks
C1 inhibitor replenishes the missing or malfunctioning C1 inhibitor. These medications are given by vein or injection under the skin.
When these medications are not available, fresh frozen plasma
Pain relievers, medications to relieve nausea (antiemetic drugs), and fluids may help relieve symptoms.
Emergency treatment
epinephrine may not reduce the swelling quickly or long enough. Then doctors insert a breathing tube in the windpipe through the person’s mouth or nose (intubation).
Sometimes doctors have to make a small incision in the skin over the windpipe (trachea) to insert the breathing tube.
Medications to prevent attacks of angioedema
Several treatments can be used to help prevent episodes of angioedema in people with hereditary C1 inhibitor deficiency. They include
C1 inhibitor derived from human blood
Synthetic male hormones
C1 inhibitor derived from human blood can be used to prevent attacks. However, recombinant C1 inhibitor cannot.
monoclonal antibody (a manufactured antibody) that targets and suppresses one of the substances involved in causing angioedema. Lanadelumab is given by injection under the skin every 2 weeks. It can be used to prevent attacks in people 12 years of age and older.
lanadelumab and is taken by mouth 3 times a day.
C1 inhibitor, but they may be less effective for acquired angioedema. Because these medications can have masculinizing side effects, the dose is reduced as soon and as much as possible when these medications are given to women for a long time.
Stanozolol or danazol may be given 5 days before until 2 days after a dental or surgical procedure. Or C1 inhibitor, if available, may be given 1 hour before dental or surgical procedures instead of stanozolol or danazol.
