Hereditary angioedema is an inherited disorder. It is caused by low levels or improper function of a protein called C1 inhibitor. This, in turn, affects 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.

There is usually a family history of the condition, but this may 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 (such as dental procedures) 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.

Because this disorder can be life-threatening and treatment options are limited, it is crucial to avoid triggers. There are no definitive studies on the outlook, as individuals differ in their patterns and severity of symptoms.

Swelling of the airways may be fatal.

Call your health care provider if you are considering having children and would like some additional information about this disorder, or if you are experiencing a group of the above symptoms.

Swelling of the airway is a life-threatening emergency. If you are having difficulty breathing due to swelling, call an emergency service in your area immediately.

Genetic counseling may be beneficial for prospective parents with a family history of hereditary angioedema.