Hereditary angioedema is an inherited disorder. It is caused by the absence of a protein called C1 inhibitor (or a defect in this protein), which in turn effects blood vessels. People with hereditary angioedema can develop rapid swelling of the hands, feet, limbs, face, intestinal tract, or airway (larynx or trachea).

Unlike an allergic reaction, there is usually no itching or hives. Swelling of the gut can cause intestinal cramping. If swelling closes the airway, it can be fatal. Attacks of swelling can become more severe in late childhood and adolescence.

A family history is usually noted, at times only reported to descendants as an unexpected, sudden, and premature death of a parent, aunt/uncle, or grandparent.

• Swelling in the arms, legs, lips, eyes, tongue, or throat
• Airway obstruction -- throat swelling and sudden hoarseness
• Repeat episodes of abdominal cramping without obvious cause
• Intestinal swelling can be severe and include vomiting, dehydration, pain, and occasionally shock

• Decreased C1 inhibiting factor activity
• Decreased C4 and C2 levels, part of the complement test

Try to prevent attacks by avoiding trauma and precipitating factors. In contrast to other causes of angioedema (e.g., from allergies), antihistamines and other related treatments are of limited benefit in hereditary angioedema.

Attenuated androgens, which are derivatives of normal sex hormones, can reduce the frequency and severity of attacks.

Once an attack occurs, treatment includes pain relief and intravenous fluids. A new treatment using C1-inhibitor concentrate is being tested.