Hereditary angioedema, although not an immunologic disorder in the usual sense, is included because of its resemblance to aller-gic angioedema and because of the seriousness of the condition. Symptoms are due to edema of the skin, the respiratory tract, or the digestive tract. Attacks may be precipitated by trauma or may seem to occur spontaneously.
When skin is involved, the swelling is usually diffuse, does not itch, and is usually not accompanied by urticaria. Gastrointestinal edema may cause abdominal pain severe enough to suggest the need for surgery. Typically, attacks last 1 to 4 days and are generally harmless. Occasionally, attacks affect the subcutaneous and submucosal tissues in the region of the upper airway and can be associated with respiratory obstruction and asphyxiation. This dis-order is inherited as an autosomal dominant trait. Approximately 85% of patients with this disorder have one nonproductive gene; the other 15% have a gene mutation (Parslow et al., 2001).
Attacks usually subside within 3 to 4 days, but during this time the patient should be observed carefully for signs of laryngeal ob-struction, which may necessitate tracheostomy as a life-saving measure. Epinephrine, antihistamines, and corticosteroids are usually used in treatment, but their success is limited.