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Skin-nontumor

Other dermatoses

Urticaria (hives)


Reviewer: Mowafak Hamodat MB.CH.B, MSc., FRCPC, Eastern Health, St. Johns (Canada) (see Reviewers page)
Revised: 1 August 2011, last major update August 2011
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.

Definition
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● Pruritic, edematous plaques (wheals) due to localized mast cell degranulation and dermal microvascular hyperpermeability
● Individual lesions fade within 24 hours, although episodes may last days to months
● Commonly at pressure points
Causes: collagen vascular disorders, Hodgkin lymphoma, allergies (mediated by IgE, bridging by multivalent ligand), IgE independent allergies (contrast dye, opiates, aspirin [suppresses prostaglandins]), hereditary angioedema (deficiency of C1 esterase inhibitor causes uncontrolled complement component activation), infections, heat, cold, pressure, vibration
Angioedema: like urticaria, but in deep dermis/subcutaneous fat

Epidemiology
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● Ages 20-40 years are most common

Clinical images
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Primary cold urticaria

Micro description
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● Age of the lesion biopsied and nature of evoking stimulus may influence type and intensity of inflammatory response
● Subtle edema (widely spaced collagen bundles), mild eosinophilic infiltrate and dilated lymphatics
● Also dilatation of small blood vessels and lymphatics, often endothelial swelling
● Cellular infiltrate is usually mild, perivascular, lymphocytes and a few eosinophils, occasional interstitial eosinophils
● No vasculitis
● Neutrophils often noted in early lesions, but relatively sparse; may be more prominent in physical urticarias
● Transmigration of neutrophils through vessel walls may resemble vasculitis, but no fibrinoid change, hemorrhage or leukocytoclasis
● In papular urticaria, inflammation is heavier than in other chronic urticarias, consists of superficial and deep perivascular lymphocytes and eosinophils

EM description
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● Platelets and other cells in lumen of mildly dilated vessels in upper dermis
● Lymphocytes and dendritic cells are close to the vessels
● Mast cells may be normal or degranulated

Additional references
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Arch Pathol Lab Med 2003;127:316 (allergic transfusion reactions)

End of Skin-nontumor > Other dermatoses > Urticaria (hives)


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