The first demyelinating event might also represent the first manifestation of a chronic demyelinating relapsing disease, such as multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD) or myelin oligodendrocyte glycoprotein antibody (MOG-Ab)-associated disease, recently recognized as a multiphasic disease course that does not resemble MS [23,24]. This evidence concerns the gene MOG and myeloid sarcoma.