Vascular obliteration because of endothelial and myointimal growth in COVID-19 patients.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is a systemic multi-organ viral illness. Previous studies have found that many patients had a procoagulant state and/or severe hypoxemia with relatively well-preserved lung mechanics. Mechanisms underlying the damage to vascular tissues are not well-elucidated yet. Histological data in COVID-19 patients are still limited and are mainly focused on post-mortem analysis. Given that the skin is affected by COVID-19 and the relative ease of its histological examination, we aimed to examine the histology of skin lesions in COVID-19 patients to better understand the disease's pathology. METHODS: Five skin lesions from COVID-19 adult patients were selected for a deep histological tissue examination. RESULTS: A strong vasculopathic reaction pattern based on prominent vascular endothelial and myointimal cell growth was identified. Endothelial cell distortion generated vascular lumen obliteration and striking erythrocyte and serum extravasation. Significant deposition of C4d and C3 throughout the vascular cell wall was also identified. A regenerative epidermal hyperplasia with tissue structure preservation was also observed. CONCLUSIONS: COVID-19 could comprise an obliterative microangiopathy consisting on endothelial and myointimal growth with complement activation. This mechanism, together with the increased vascular permeability identified, could contribute to obliteration of the vascular lumen and hemorrhage in COVID-19. Thus, anticoagulation by itself could not completely reverse vascular lumen obliteration, with consequent increased risk of hemorrhage. Findings of this study could contribute to a better understanding of physiopathological mechanisms underlying COVID-19 on living patients and could help further studies find potential targets for specific therapeutic interventions in severe cases.