Although we do not have a trustworthy explanation for the shorter incubation period (7.5 vs. 14 days), smaller diameter of EM (10.5 vs. 15.5 cm), and more frequent presence of symptoms/signs indicating or suggesting borrelial dissemination (18.8% vs. 0%) in immunocompromised vs immunocompetent patients, these findings could be related to treatment with TNF-α inhibitors. This evidence concerns the gene TNF and erythema multiforme.