Myelin oligodendrocyte glycoprotein antibody associated disease (MOGAD) defines a subgroup of patients with central nervous system (CNS) inflammation with MOG-IgG that is distinct from multiple sclerosis (MS) and aquaporin-4 (AQP4)-IgG positive neuromyelitis optic spectrum disorder (NMOSD). The gene discussed is MOG; the disease is myeloid sarcoma.