What is Hereditary Angioneurotic Edema?

Hereditary angioneurotic edema is an uncommon genetic condition that causes major swelling in different parts of the body. The disorder typically first causes symptoms in childhood, and episodes of swelling tend to worsen and become more frequent after puberty. Hereditary angioneurotic edema most commonly leads to swelling in the extremities and face that may be uncomfortable but generally are not life-threatening. If the condition affects the airways and gastrointestinal tract, however, potentially severe complications can arise. There is no clear cure, but doctors can provide medications and clinical treatments to manage symptoms when episodes occur.

Recent research has pinpointed the underlying genetic factors involved in hereditary angioneurotic edema. In healthy people, the SERPING1 gene produces proteins called C1 inhibitors that play a major role in controlling inflammation and swelling. Patients with hereditary angioneurotic edema have either inactivated or abnormally functioning SERPING1 genes. Their low levels of C1 inhibitors lead to blood vessel inflammation and damage, which allows fluid to seep from the vessels and collect in body tissue. The result is severe, frequent swelling episodes in one or more areas of the body at a time.

As the name suggests, hereditary angioneurotic edema can be passed down from parents. It is an autosomal dominant disorder, which means that only one parent needs to possess a damaged copy of the gene in order to pass it down. It is possible, however, for a new, random mutation to cause angioneurotic edema in a person who has no family history of the condition or any other type of autoimmune disorder.

The type and severity of symptoms depend on which body parts are affected. Many patients experience swelling in their arms, legs, and face. Pain and tenderness are uncommon, though it may be difficult to wear shoes, walk, or perform hands-on tasks when swelling is present. Hereditary angioneurotic edema may affect the intestines as well, leading to stomach cramps, nausea, vomiting, diarrhea, and other related symptoms. Throat and tongue swelling are major concerns as well because they can cause life-threatening breathing difficulties.

Since swelling can be a symptom of many different health problems, it can be difficult to obtain a clear diagnosis of angioneurotic edema. Doctors generally review a patient's medical and family history and rule out other potential causes, such as infections and allergies. Genetic testing on blood samples can confirm the diagnosis after other problems have been dismissed.

Most edema episodes can be controlled with a drug called danazol, which improves C1 protein levels in the bloodstream. People who experience frequent problems are often instructed to take low doses of danazol daily to help prevent attacks. Emergency treatment may be necessary for airway or intestinal swelling. Breathing tubes, oxygen therapy, and intravenous nutrition can keep patients stable until their symptoms improve.