The other theory is a toxic effect, causing endothelial dysfunction and vasoconstriction that subsequently leads to edema.8 In such a way, infliximab, which binds to TNF-alpha, by antibody-dependent cellular toxicity or complement-dependent cytotoxicity, can lead to cell destruction and edema, which could be the mechanism behind PRES.9 In this case, hypertension was noted as the first manifestation, supporting the first theory. This evidence concerns the gene TNF and Posterior Leukoencephalopathy Syndrome.