Recent studies by us and others have demonstrated the presence of IgG antibodies to myelin oligodendrocyte glycoprotein (MOG-IgG) in a subset of patients with NMO as well as in patients with isolated ON or longitudinally extensive transverse myelitis (LETM), syndromes that are often formes frustes of NMO [10–12]. The gene discussed is OMG; the disease is neuromyelitis optica.