Background: Severe coronavirus disease 2019 (Covid-19) is a systemic multi-organ viral invasion. Previous studies found that many patients had a procoagulant state and/or severe hypoxemia with relatively well-preserved lung mechanics. Mechanisms underlying the vascular and its surrounding tissue are not well known yet. Histological data in Covid-19 tissues´ patients are still limited and mainly focused on post-mortem analysis. Since SARS-CoV-2 largely affects cutaneous tissue, we aim to assess the pathophysiologic mechanisms in depth in living skin tissue related to Covid-19.
Methods: Five skin lesions from caucasian Covid-19 adult patients were selected for cutaneous tissue histological examination including immunohistochemistry (IHC) and direct immunofluorescent (DIF) vast amount of data.
Results: A common strong vasculopathic reaction pattern based on prominent vascular endothelial and myointimal cellgrowth was identified. Endothelial cell distortion generated vascular lumen obliteration and a strike erythrocyte and serum extravasation. Extensive significant vascular C4d and C3 deposition throughout vascular cell wall was also identified. A regenerative epidermal hyperplasia with tissue structure preservation was also found.
Conclusions: Covid-19 could comprise an obliterative micro-angiopathy consisting on endothelial and myointimal intensive growth with complement activation. This mechanism, together with increased vascular permeability identified, could contribute to obliterative vascular lumen and hemorrhage in Covid-19 disease. Activation of the complement and angiogenic pathways could have an important role in inducing and maintaining this vasculopathic reaction pattern. Thus, anticoagulation by itself could not completely reverse vascular lumen obliteration, with consequent hemorrhagic increased risk associated. Skin is the largest organ in the body, the most accessible one and can mirror other organs of the body. Findings of this study could contribute to a better understanding of physio-pathological mechanisms underlying Covid-19 infection on living tissue and could help further studies find potential targets for specific therapeutic interventions in Covid-19 severe patients.