HAE Overview

Hereditary angioedema (HAE) is a rare, potentially fatal genetic disorder typified by a deficiency or dysfunction of the plasma protein C1 Inhibitor, and characterized clinically by swelling of the extremities, face, trunk, abdominal viscera, and upper airway¹. Abdominal attacks can cause severe pain, and mortality from edema induced airway closure has been reported to be as high as 30% in affected kindreds.

Although urticaria and angioedema are fairly common problems that affect nearly 20% of the population, HAE is an extremely rare disease that accounts for about 2% of clinical angioedema cases². The vast majority of patients who experience episodic swelling will be diagnosed with histamine mediated allergic angioedema. Epidemiological estimates peg the incidence of HAE at 1/10,000 to 1/50,000 individuals.

In contrast to allergic angioedema, HAE-related swelling is caused by an autosomal dominant genetic defect that results in compromised functional levels of the plasma protein C1 inhibitor³. Because defective C1-inhibitor does not adequately perform its normal regulatory function, a biochemical imbalance can occur and produce a vasoactive peptide that induces the capillaries to release fluids into surrounding tissues, thereby causing edema.

A child has a 50 percent chance of inheriting this disease if a parent possesses the genetic defect, however, the absence of family history does not rule out the HAE diagnosis. Scientists report that as many as 25 percent of newly diagnosed HAE cases result from de novo mutations of the C1-inhibitor gene at conception⁴.