Urticaria has been recognized since the days of Hippocrates. The name of the condition dates back to the 18th century, when the burning and edema of the skin was likened to that caused by contact with nettles (Urtica dioica). Urticaria affects 10% to 25% of the population worldwide at some point in their lives.1 The condition is characterized by short-lived edema of the skin, mouth, and genitalia related to a transient leakage of plasma from small blood vessels into the surrounding connective tissues. Urticaria may present with superficial edema of the dermis (wheals) or deeper edema of the dermal, subcutaneous, or submucosal tissues (angioedema).2 Wheals typically are itchy with a pale center, maturing into pink superficial plaques. Areas of angioedema tend to be pale and painful; last longer than wheals; and may involve the mouth and rarely the bowel.
Case Report
A 40-year-old woman in otherwise good health presented with a 5-year history of recurrent pruritic light red lesions on her chest and back. She reported that individual lesions would last up to 24 hours in one area before disappearing, while other new crops of lesions would develop in other areas of her body. She had no associated facial edema or lip or throat involvement, and she denied taking any medications. Her history failed to reveal any potential triggers for the eruptions. On physical examination, multiple elevated superficial erythematous papules and plaques were noted, with shapes varying from annular to circinate, areas of central clearing, and targetlike lesions on the trunk and extremities. The lesions blanched with pressure (Figure). The woman had no mucosal involvement, scars, or change in pigmentation. Results from the remainder of the physical examination were unremarkable.
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Because of the extent of involvement and the erythematous to violaceous aspect of certain lesions, a 3-mm punch biopsy was performed to rule out urticarial vasculitis. Histology results were consistent with urticaria with red blood extravasation but without vasculitis. Our patient initially was treated with topical clobetasol propionate ointment, 10 mg of cetirizine hydrochloride, and topical calamine lotion. At follow-up one week later, she mentioned that she had improved after 5 days of treatment but began developing new lesions 2 days prior to her second visit. Given the severity of pruritus and after a discussion of the role of corticosteroids for acute urticaria, a taper dose of prednisone was prescribed at 40 mg/d, in addition to 60 mg of fexofenadine hydrochloride twice daily. The patient was lesion- and symptom-free after 7 days of treatment, with no recurrence one month later.
Comment
Urticaria may be acute or chronic. Acute urticaria is idiopathic in more than 50% of patients but can occur as a type 1 hypersensitivity reaction to food or wasp or bee stings; an immunologic response to blood products, infection, or febrile illness; or an adverse effect of drug therapy by various mechanisms, such as penicillin or angiotensin-converting enzyme inhibitors.3 As opposed to acute urticaria, chronic urticaria is defined by recurrent episodes occurring at least twice weekly for 6 weeks.2 Urticaria occurring less frequently than this, over a long period, is more accurately termed episodic because it is more likely to have an identifiable environmental trigger. All chronic urticaria implicitly go through an acute stage (<6 weeks). Although many classification systems of chronic urticaria exist, a concise clinical classification is included in the Table.2 Urticarial vasculitis is a small vessel vasculitis but is included in the classification because it is clinically indistinguishable from other urticarial lesions.
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Urticarial lesions in chronic urticaria typically last 4 to 36 hours and can occur in individuals of any age (though it is most common in women), usually with few systemic symptoms.4 Pruritus is nearly always severe, especially at night, and may prevent sleep. Fifty percent of cases resolve spontaneously by 6 months, but of those that do not, 40% still have symptoms of urticaria 10 years later.4 The severe effect of chronic urticaria on quality of life often is underestimated.5
Ordinary Urticaria
Patients previously classified as having chronic idiopathic or "ordinary" urticaria are now divided into 2 groups: 50% to 60% of these patients have chronic idiopathic urticaria (CIU), and the remainder have chronic autoimmune urticaria (CAU).6 Results from a study in children demonstrated that autoimmune urticaria occurs in children in as many as 30% of chronic cases.7 CAU is caused by an immunoglobulin (Ig) G antibody to the α subunit of the IgE receptor (35%–40% of cases) or to IgE (5%–10% of cases).6 The IgG subclasses that appear to be pathogenic are IgG1; IgG3; and, to a lesser degree, IgG4 (though not IgG2).6 Complement activation augments histamine secretion by release of C5a.8 CAU has been reported to be associated with antithyroid antibodies (27% of cases)6,9; autoimmune conditions such as vitiligo, rheumatoid arthritis, and pernicious anemia; and low vitamin B12 levels.10 Patients with demonstrable histamine-releasing autoantibodies have a very strong association with HLA-DR4 and its associated allele HLA-DQ8.11