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Congenital angioedema: causes, symptoms, diagnosis, treatment
Last reviewed: 07.07.2025
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Hereditary angioedema is a consequence of deficiency (type 1, in 85% of cases) or dysfunction (type 2, in 15% of cases) of the C1 protein inhibitor, which regulates complement activation via the classical pathway.
Inherited in an autosomal dominant manner. C1 inhibitor deficiency develops when complement is consumed in neoplastic processes or when autoantibodies to C1 inhibitor are produced in monoclonal gammopathies (acquired deficiency). Attacks are provoked by trauma, viral infection, and are exacerbated by emotional stress.
Symptoms and signs are the same as those of angioedema, except that the edema progresses until the complement components are exhausted; the gastrointestinal tract is often affected, with nausea, vomiting, colic, and signs of intestinal obstruction.
The diagnosis is based on the detection of low levels of C2 and C4 (substrates of C1 inhibitor), normal levels of C1q (a fragment of C1), and decreased function of C1 inhibitor. In type 1 of the disease, C1 inhibitor levels are low; in type 2, they are normal or elevated. In acquired C1 inhibitor deficiency, C1q levels are low.
Treatment is with soluble androgens (eg, stanozolol 2 mg orally three times daily or danazol 200 mg orally three times daily) to stimulate hepatic synthesis of C1 inhibitor. Some experts recommend administration of fresh frozen plasma immediately before dental or other medical procedures to prevent attacks, but this approach is not routinely used and may theoretically provoke attacks by introducing substrates for edema. Purified C1 inhibitor and recombinant C1 inhibitor are under development for rescue therapy.
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