Which histologic findings are characteristic of urticarial vasculitis?

Updated: Sep 16, 2020
  • Author: Darius Mehregan, MD; Chief Editor: Dirk M Elston, MD  more...
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On biopsy, histologic findings are those of a leukocytoclastic vasculitis, defined as damage to the small vessels in the papillary and reticular dermis (see images below). [24]

A low-power histologic image of urticarial vasculi A low-power histologic image of urticarial vasculitis shows leukocytoclastic vasculitis with damage to the vessel wall and a neutrophilic infiltrate.
A high-power view of the histology of urticarial v A high-power view of the histology of urticarial vasculitis shows extensive fibrin deposition in the vessel walls. Surrounding the vessels is a mixed infiltrate predominately composed of neutrophils with leukocytoclasis.

Early lesions show a perivascular neutrophilic infiltrate involving postcapillary venules. Leukocytoclasis is present, expansion of the vessel wall occurs, and the endothelium is intact. Eosinophils may be noted early. Fibrin deposition and extravasation of red blood cells ensue.

Later in the lesion's course, infiltrate may become a mixture of lymphocytes and neutrophils. Consider performing direct immunofluorescence on the skin biopsy, which may show deposition of complement and fibrin in the blood vessels and, occasionally, immunoglobulin M, immunoglobulin G, and immunoglobulin A along the basement membrane zone of the skin.

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