AQP4 and myeloid sarcoma: Atypical ON is usually associated with autoimmune disorders, out of MS, with particular regard to anti-aquaporin 4 (AQP4) antibodies disease or neuromyelitis optica spectrum disease (NMOSD) and anti-myelin oligodendrocyte glycoprotein (MOG) antibodies associated disease (MOGAD); these conditions are potentially much more vision-threatening and often lead to the necessity of long corticosteroid treatment or plasma exchange [8].