ISG15 and COVID-19: Transcriptional similarities between COVID-19 and CLE samples were based on the expression of IFNs (IFNA2, IFNA4, IFNA1, IFNA13, IFNB1, IFNL2 and IFNL3) in purpuro-necrotic COVID-19 skin lesions and IFN-stimulated genes (ISGs) (IFIT2, BST2, IRF7, OASL, MX1, IFITM1, IFIT2, IFI35, IFIH1, ISG15, CXCL10 and CXCL9) in those with a maculo-papular phenotype (Fig. 1a).