MPO and neuromyelitis optica: Serum testing returned negative for Neisseria meningitidis, streptococcus pneumoniae, syphilis, tuberculosis, toxoplasmosis, HSV, VZV, enterovirus, ACE, anti-double stranded deoxyribonucleic acid, ANA, anti-myeloperoxidase (MPO) antibody, beta-2 glycoprotein IgG antibody, anti-cyclic citrullinated peptide (anti-CCP), myelin oligodendrocyte glycoprotein (MOG) antibody, neuromyelitis optic (NMO) antibody and human leukocyte antigens (HLA) B51.