Angioedema

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In medicine and immunology, angioedema is type of hypersensitivity that is a "swelling involving the deep dermis, subcutaneous, or submucosal tissues, representing localized edema. Angioedema often occurs in the face, lips, tongue, and larynx."^[1] Angioedema of sudden onset, as in anaphylaxis, can be a life-threatening respiratory emergency.

Causes[edit]

Among patients with recurrent angioedema without urticaria, 38% are idiopathic, 25% are due to deficiency of functional complement C1 inhibitor protein (C1 esterase inhibitor), 16% are related to an environmental exposure (medication, foodstuff, insect bite, other environmental allergen, or physical irritation), and 11% are due to angiotensin-converting enzyme inhibitor treatment.^[2]

C1 esterase inhibitor deficiency[edit]

Angioedema due to deficiency of functional complement C1 inhibitor protein manifest by edema without urticaria, without pruritis^[3][4][5] and may be reduced have reduced d-dimer levels, especially during attacks.^[6]

Hereditary angioedema (Hereditary C1 esterase inhibitor deficiency)[edit]

For more information, see: Hereditary angioedema.

Hereditary deficiency is characterized by normal levels of complement C1q and complement C1 inhibitor protein function.^[5] Complement C1 inhibitor protein antigen is low in type I and normal in type II.

Acquired angioedema (Acquired C1 esterase inhibitor deficiency)[edit]

Acquired C1 esterase inhibitor deficiency is rare.^[4][5]

• Type I disease is associated with lymphoproliferative disorders.^[5]
• Type II disease is associated with autoantibodies^[5] and monoclonal gammopathies^[7].

Acquired deficiency is characterized by low levels of complement C1q.^[5] Like hereditary angioedema, it has low complement C1 inhibitor protein function.^[5] Complement C1 inhibitor protein antigen is low in type I and normal in type II. It also has decreased complement C4^[8] (the second most abundant complement protein in serum, and a principal effector of inflammatory reactions) unless a paraprotein is present^[9].

Treatment includes oral tranexamic acid oral 1 gram 3 times a day. Tranexamic acid is an "inhibitor of plasminogen activation, and at much higher concentrations, a noncompetitive inhibitor of plasmin, i.e., actions similar to aminocaproic acid." It is similar to, but more potent than aminocaproic acid.^[10] Concomittent use of warfarin may be needed to prevent embolism and thrombosis.

Insect bite[edit]

Angioedema may be due to insect bites.^[11]

The risk of subsequent systemic anaphylaxis is 5% to 15% according to a review^[11] that cites several case series.^{[12][13][14][15][16]} This risk may be increased in patients with a positive skin test^[13] or elevated I_gE to bee venom.^[17]

Immunotherapy may reduce the size and duration of subsequent episodes.^[18]

Treatment[edit]

Protecting the airway is of first importance. If there is any significant compromise, admit the patient to an intensive care unit; otherwise observe in an emergency room. Discontinue all potentially causative drugs.

Provide supplemental oxygen and monitor oxygenation. If the airway is compromised, protect it with appropriate intubation or other intubation, and administer 1:1000 epinephrine subcutaneously or intramuscularly every 10 minutes.

Give antihistamines and corticosteroids.^[19]

References[edit]