Urticarial vasculitis: Clinical and laboratory findings with a particular emphasis on differential diagnosis.

Urticarial vasculitis (UV) is a rare cutaneous vasculitis of small vessels characterized by recurrent episodes of wheal-like lesions that tend to last more than 24 hours, healing with a residual ecchymotic postinflammatory hyperpigmentation. The histopathologic pattern of UV is that of leukocytoclastic vasculitis, consisting of fibrinoid necrosis of dermal vessels' walls and neutrophil-rich perivascular inflammatory infiltrates. Although its etiopahogenesis remains still undefined, UV is now regarded as an immune complex-driven disease with activation of the complement cascade, leading to exaggerated production of anaphylatoxins that are responsible for neutrophil recruitment and activation. This condition can be categorized into 2 main entities according to serum complement levels: normocomplementemic UV and hypocomplementemic UV, the latter being associated with circulating anti-C1q autoantibodies and possible extracutaneous manifestations. Systemic multiorgan involvement may be seen particularly in syndromic hypocomplementemic UV, also known as McDuffie syndrome. This review summarizes the clinicopathological and laboratory features as well as the underlying pathophysiological mechanisms of UV. A focus on its main differential diagnoses is provided, that is, chronic spontaneous urticaria, bullous pemphigoid, IgA (Henoch-Schönlein purpura) and IgM/IgG immune complex vasculitis, lupus erythematous tumidus, Wells syndrome, erythema multiforme, cutaneous mastocytosis, cryopyrin-associated periodic syndromes, and coronavirus disease 2019-associated and anti-severe acute respiratory syndrome coronavirus 2-vaccine-associated urticarial eruptions.

Leukocytoclastic vasculitis (cutaneous small-vessel vasculitis) after COVID-19 vaccination.

Vaccinations may induce cutaneous adverse events, due to nonspecific inflammation or immuno-mediated reactions. Several types of vasculitis have been observed. We report on a 71-year-old woman who developed cutaneous small-vessel vasculitis after the second dose of Vaxzevria COVID-19 vaccination, showing leukocytoclastic vasculitis on histopathological examination of a skin biopsy. Cutaneous small-vessel vasculitis is a rare condition which can be idiopathic or secondary to underlying infections, connective tissue disorders, malignancy, and medications. The pathogenesis involves immune complex deposition in small blood vessels, leading to activation of the complement system and recruitment of leukocytes. Exacerbation of small-vessel vasculitis has been reported following the administration of various vaccines, particularly influenza vaccine. It is expected that SARS-CoV-2 vaccine results in the activation of B- and T-cells and antibody formation. We hypothesize that leukocytoclastic vasculitis caused by immune complex deposition within cutaneous small vessels could be a rare side effect of Vaxzevria COVID-19 vaccination.

Leucocytoclastic vasculitis in a patient with COVID-19 with positive SARS-CoV-2 PCR in skin biopsy.

Main skin manifestations of COVID-19 have been recently classified. However, little is known about cutaneous histopathological patterns and the presence of SARS-CoV-2 in these skin lesions. We present a healthy 29-year-old man who developed a leucocytoclastic vasculitis for COVID-19 with positive SARS-CoV-2 PCR in skin biopsy.