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Chronic urticaria is normally defined as daily or almost daily urticaria for more than 6 weeks. Chronic urticaria has been traditionally subdivided into physical urticaria (wheals evoked by a physical stimulus, such as pressure, friction, cold contact, or sun exposure) and spontaneous urticaria.
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A patient with a length of history less than 6 weeks is designated as having acute urticaria, although most patients with acute urticaria have a much shorter duration.
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Depletion of the peripheral blood
Pathology and Classification of Urticaria
Section snippets
Key points
What is urticaria?
In 1480, King Richard III of England, whose mortal remains have recently been discovered under a public car park in Leicester, developed an itchy red rash after consuming strawberries procured by a courtier. Accused by the king of witchcraft, the courtier was put to death.1 Fortunately, even when accompanied by angioedema, urticaria is rarely fatal. The term, urticaria, was first used by Johann P Frank in 1792 in his classic De curandis hominum morbus epitome praelectionibus dicata. Aided by
The dermal mast cell in urticaria
Despite their central role in the pathogenesis of urticaria, histologic studies have not convincingly demonstrated quantitative or qualitative abnormalities in dermal mast cells in any subtype of urticaria. Using a double-labeling immunohistochemical technique, no significant difference in mast cell numbers in lesional, nonlesional, or control (healthy) skin were observed.9 Human mast cells are of 2 types, based on the protease content of the granules. Mast cells of the Tc type (MC Tc) contain
The basophil leukocyte in urticaria
It has long been recognized that depletion of the peripheral blood basophil leukocyte count occurs in some patients with chronic spontaneous urticaria.13, 14 This abnormality is strongly associated with the presence of functional IgG anti-FcɛR1 autoantibodies (autoimmune chronic urticaria), suggesting active recruitment of blood basophils into lesional skin.15, 16, 17 Circulating basophils in patients with chronic urticaria show reduced reactivity to activation via the high-affinity IgE
The inflammatory infiltrate in chronic urticaria
That the inflammatory infiltrate plays a major role in the pathogenesis of chronic spontaneous urticaria (CSU) is evidenced by the almost invariably positive response to systemic corticosteroids, which have little or no direct effect on dermal mast cells. Conversely, physical urticarias, such as symptomatic dermographism, in which there is little or no perivascular infiltrate, respond poorly if at all to systemic corticoids.
The dermal perivascular infiltrate of lesional skin in CSU contains
Pharmacologic mediators of chronic urticaria
The wheals of physical urticarias, including symptomatic dermographism and cold contact urticaria, are short-lived and closely resemble the triple response of skin to intradermal injection of histamine (central wheal, erythema, and an axon flare)5 together with itching. This, and the effective suppression of symptoms and signs by H1 antihistamines encourages the view that histamine, derived from dermal mast cells, is the main, if not the only, mediator of these physical urticarias. As indicated
Pathophysiology of itch in urticaria
Itch is the dominant symptom of urticaria. Most patients with urticaria rub rather than scratch their itchy wheals. In the urticaria clinic, prominent excoriation is a rarity, which, if present, calls into question the diagnosis. Itch is usefully classified as pruritogenic (generated in the skin), neurogenic (generated in the central nervous system in response to circulating pruritogens), neuropathic (due to anatomic lesions in the peripheral or central nervous sytem), and psychogenic (stress
Autoimmunity in chronic urticaria
A close association between chronic urticaria and autoimmune disease has long been recognized. In the 1980s, Leznoff drew attention to the frequent occurrence of autoimmune thyroid disease and chronic urticaria. Of 182 patients with chronic urticaria, 22 (12%) had antithyroid microsomal autoantibodies. Leznoff went as far as to propose a syndrome of autoimmune thyroid disease and chronic urticaria.49, 50, 51 In a recent large Israeli study, chronic urticaria was associated with an increased
Classification of urticaria
To describe a patient as having urticaria and/or angioedema is not to make a diagnosis but rather to characterize in a general way the signs and symptoms that the patient has. The subtypes of urticaria are different in etiology, pathogenesis, prognosis, and treatment. Classification of urticaria is only of value if it aids clinicians in formulation of an investigational and therapeutic strategy for individual patients. An internationally recognized classification should also be useful to
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