RNA of SARS-CoV-2 receptors but no virus in COVID-MDR lesional skin
The distinct cellular and molecular signature in COVID-MDR suggested that COVID-19 may impact this reaction in the skin. A SARS-CoV-2 PCR on RNA turned out negative for all COVID-MDR skin samples. We then investigated the expression of the known SARS-CoV-2 receptors ACE2, Transmembrane protease, serine 2 (TMPRSS2), BSG (Basigin; CD147), and DPP4 (Dipeptidyl peptidase-4, CD26)27-29. We did not find any difference in keratinocyte ACE2 expression between COVID-MDR, DRESS and MDR on a protein level by IHC staining (Figure S2). On the gene expression level however, ACE2 and DPP4 but not other receptor-related molecules were upregulated in COVID MDR compared to HC (Figure 4D, S4).