Symptoms and signs are similar to those of other forms of bradykinin-mediated angioedema, with asymmetric and mildly painful swelling that often involves the face, lips, and/or tongue. Swelling may also occur on the back of hands or feet or on the genitals.

The GI tract is often involved, with manifestations that suggest intestinal obstruction, including nausea, vomiting, and colicky discomfort.

Pruritus, urticaria, and bronchospasm do not occur, but laryngeal edema may be present, causing stridor (and sometimes death).

Swelling resolves within about 1 to 3 days of onset. In hereditary angioedema, symptoms resolve as complement components are consumed.

Levels of C4, C1 inhibitor, and C1q (a component of C1) are measured. Hereditary angioedema (types 1 and 2) or acquired C1 inhibitor deficiency is confirmed by

Other findings include

If angioedema is not accompanied by urticaria and recurs without any clear cause, clinicians should suspect hereditary angioedema or acquired C1 inhibitor deficiency. If family members have it, they should suspect hereditary angioedema.

Acute attacks are treated with purified human C1 inhibitor, ecallantide, or icatibant. If none of these drugs is available, fresh frozen plasma or, in the European Union, tranexamic acid has been used. A recombinant form of C1 inhibitor (recombinant human C1 esterase inhibitor [rhC1INH], or conestat alfa) is available in Europe.

If the airways are affected, securing an airway is the highest priority. Epinephrine may provide transient benefit in acute attacks when airways are involved. However, the benefit may not be sufficient or may be temporary; then endotracheal intubation may be necessary. Corticosteroids and antihistamines are not effective.

Analgesics, antiemetics, and fluid replacement can be used to relieve symptoms.

For long-term prophylaxis, attenuated androgens (eg, stanozolol 2 mg po tid, danazol 200 mg po tid) are used to stimulate hepatic C1 inhibitor synthesis. This treatment may be less effective for the acquired form. C1 inhibitor is effective but expensive.

Short-term prophylaxis is indicated before high-risk procedures (eg, dental or airway procedures) if C1 inhibitor is not available to treat an acute attack. Patients are usually given attenuated androgens 5 days before the procedure until 2 days afterward. If C1 inhibitor is available, some experts advocate giving it 1 h before high-risk procedures rather than attenuated androgens for short-term prophylaxis.