Persistent SARS-CoV-2 Spike Protein in Vasculitic Skin Lesions after Infection or mRNA Vaccination: A Retrospective Case control Immunofluorescence Study

Vasculitic skin lesions have been reported in association with both SARS-CoV-2 infection and vaccination. Whether viral proteins persist in lesional vessels beyond the acute phase remains unclear. The aim of this study was to investigate the presence of SARS-CoV-2 spike protein in persistent or delayed-onset cutaneous vasculitis temporally associated with COVID-19 infection or vaccination. This retrospective case-control study includes 9 patients with persistent or delayed-onset vasculitic skin lesions following COVID-19 infection (n=4) or mRNA vaccination (n=5). Skin biopsies were analysed using immunofluorescence for SARS-CoV-2 spike protein. Prepandemic leukocytoclastic vasculitis (n=3) and healthy postinfection/postvaccination skin (n=3) served as controls. Spike protein was detected in vascular endothelial cells of all 9 patients with COVID-19- or vaccine-associated vasculitis. Staining was absent in all prepandemic vasculitis and healthy control samples. Histopathology showed typical features of leukocytoclastic vasculitis without evidence of viral cytopathic changes. We found that SARS-CoV-2 spike protein can persist in endothelial cells of vasculitic skin lesions weeks to months after COVID-19 infection or mRNA vaccination. These findings suggest that retained viral proteins may contribute to prolonged or delayed-onset vasculitic skin manifestations. Further studies are needed to clarify the mechanisms underlying spike persistence and its clinical significance.