Urticaria and Angioedema

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14

Urticaria and Angioedema

Urticaria and angioedema can occur at any age and are estimated to have an overall lifetime prevalence of 10–25%.

Urticaria (hives) is characterized by wheals: evanescent, pale to pink-red, edematous papules or plaques (Fig. 14.1); lesions often have central clearing, a peripheral erythematous flare, and associated pruritus.

Individual wheals last <24 hours, which can be documented by outlining them with ink.

Angioedema represents deeper dermal and subcutaneous or submucosal swelling (Fig. 14.2); affected areas are ill-defined, have minimal or no overlying erythema, and may be painful as well as pruritic.

In addition to the skin/subcutis, angioedema can affect the mouth and respiratory or gastrointestinal tract; an area of swelling may persist for several days.

A classification scheme and DDx for urticaria and angioedema are presented in Table 14.1; patients with angioedema may have associated urticaria, including physical urticaria.

Urticaria and urticaria-associated angioedema result from the release of histamine and other proinflammatory and vasoactive substances from mast cells; this leads to extravasation of plasma, vasodilatation, and pruritus.

Stimuli for mast cell degranulation are shown in Fig. 14.3.

Spontaneous (‘Ordinary’) Urticaria: Acute and Chronic

Although both can occur at any age, acute urticaria is most common in children, whereas chronic urticaria has a peak in the fourth decade of life and a female : male ratio of ~2 : 1.

The most frequent causes of acute and chronic urticaria are listed in Table 14.2.

Acute urticaria in young children often presents with large annular or polycyclic lesions (urticaria ‘multiforme’; see Figs. 14.1B and 3.3A) that tend to resolve with a transient dusky purplish hue, which can lead to misdiagnosis as erythema multiforme.

Urticaria can result in sleep disturbances and anxiety.

Chronic autoimmune urticaria is associated with an increased risk of other autoimmune conditions, such as thyroid disorders and celiac disease.

An approach to the diagnosis of chronic urticaria is outlined in Fig. 14.4; extensive laboratory evaluations (e.g. for food allergies) are extremely low-yield and are not recommended.

Rx: a stepwise therapeutic approach is presented in Fig. 14.5; long-acting antihistamines are the mainstay of treatment, and systemic corticosteroids should be avoided.

Physical (Inducible) Urticaria

Delayed Pressure Urticaria

Pruritic and/or painful erythema and swelling (Fig. 14.7) develop 0.5–12 hours after sustained pressure to the skin (e.g. due to tight clothing or shoes); may last several days, sometimes with associated arthralgias and malaise.

Hereditary Angioedema (HAE)

HAE due to deficiency (type I) or dysfunction (type II) of the complement C1 esterase inhibitor is an uncommon autosomal dominant disorder that presents with episodic nonpruritic angioedema lasting 2–3 days, often beginning in early childhood and triggered by trauma; although not associated with true urticaria, attacks are occasionally preceded or accompanied by transient, nonpruritic, serpiginous erythematous patches.

Type I/II HAE favors the extremities and gastrointestinal tract (may mimic an acute abdomen), and airway compromise due to laryngeal edema can occur.

Type III HAE is a later-onset form with more frequent facial involvement that develops primarily in teenage girls and young women.

Pathogenesis of HAE is related to excessive generation of bradykinin, which leads to increased vascular permeability.

Evaluation and DDx: outlined in Fig. 14.9.

Rx: acute attacks or short-term prophylaxis (e.g. for surgical or dental procedures) – intravenous C1 inhibitor concentrate > subcutaneous ecallantide (kallikrein inhibitor) or icatibant (bradykinin B2 receptor antagonist); long-term treatment – androgens (e.g. oral danazol) > antifibrinolytic agents; antihistamines, epinephrine, and corticosteroids are not effective.

For further information see Ch. 18. From Dermatology, Third Edition.