How are the different types of chronic urticaria characterized?

Updated: Jul 31, 2018
  • Author: Marla N Diakow, MD; Chief Editor: William D James, MD  more...
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Answer

About 20% of patients with chronic urticaria have physical urticaria, in which the appearance of lesions is triggered by a consistent identifiable factor. Physical urticaria is reproducible with the appropriate stimuli, and it can be identified with a thorough history, physical examination, and challenge testing. Some examples of direct triggers include mechanical stimuli, temperature changes, sweating, stress, sun exposure, and water contact.

When a physical etiology has been excluded, the traditional approach has been to order a panel of laboratory tests to uncover an occult medical condition responsible for the skin findings. In many patients, an extensive workup does not uncover an etiology. In systematic review of 6462 patients with chronic urticaria, a causative internal medical condition was found in only 1.6% of patients [6] .Urticaria rarely is the sole manifestation of an underlying medical problem.

The largest subset of patients with chronic urticaria encompasses patients in whom no explanation for their urticaria is definitively established. Traditionally, these patients were said to have chronic idiopathic urticaria; however, findings suggest that about 20-45% of such patients may have an underlying autoimmune process driving their disease, and this specific cohort of patients is said to have chronic autoimmune urticaria. Chronic spontaneous urticaria is a newer label used to refer to all patients with either chronic idiopathic urticaria (55%) or chronic autoimmune urticaria (45%). [7]

An important entity in the differential diagnosis of chronic urticaria is urticarial vasculitis. A forme fruste of leukocytoclastic vasculitis, urticarial vasculitis may be associated with hypocomplementemia and systemic symptoms. If urticarial lesions persist for more than 24 hours, biopsy should be performed to rule out this entity histologically.


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