Clinical and morphological specifics, pathogenetic ways of skin manifestations in SARS-CoV-2 infection

To date, the most studied clinical and morphological changes characteristic of SARS-CoV-2 virus are its pulmonary manifestations and cardiovascular involvement. However, the evaluation of COVID-associated skin changes and the analysis of their mechanisms are also important for us, because the skin manifestations of the infection can change the patient's appearance for the worse, i.e. affect the aesthetic sphere and significantly reduce the quality of life. The study of not only skin manifestations of COVID-19, but also their morphological substrate and pathogenetic basis allows us to apply the most effective methods of treatment and provide adequate management of patients even in the post-coital status.

According to the information collected to date, the most frequently reported skin manifestations of SARS-CoV-2 are pseudo-frostbite, maculopapular and vesicular lesions, urticaria, lividoid and necrotic lesions, hemorrhagic purpura (vasculitis), and conditions from the group of other unclassified skin lesions. Despite the variety of clinical variants of SARS-CoV-2-associated skin changes, morphological stigmas are often stencil-like: these are areas of lymphohistiocytic infiltration of perivascular localization, the presence of fibrinoid necrosis foci in the vessel walls, the formation of occlusive thrombi, erythrocyte extravasation. Mechanisms of damage to epidermis and dermis within COVID-19 infection may be due to the influence of complement components, activation of cytotoxic lymphocytes and NK-cells, excessive synthesis of proinflammatory cytokines, in particular, interleukin 6, as well as interferons, hyperergic reactions. In addition to routine morphological, immunohistochemical examination of skin biopsy specimens from patients with different forms of skin manifestations of SARS-CoV-2 infection is an important tool in the diagnostic confirmation of COVID-associated dermatologic pathology, especially in patients with a suspected history of this disease or with problematic laboratory results.