NMO spectrum of disorders: A paradigm for astrocyte-targeting autoimmunity and its implications for MS and other CNS inflammatory diseases

When studying a rare or orphan disease, we hope to shed light on more prevalent syndromes. Neuromyelitis optica (NMO), also known as Devic's disease, is a rare disease with a prevalence of about 4 in 100,000. Since 2005 when the anti-Aquaporin 4 (AQP4) NMO autoantibody was discovered by Lennon's group at the Mayo clinic, an enormous amount of data have been acquired on the pathogenesis of the disease. A review of the literature showed 47 relevant publications in 2004, compared with 353 in 2013. The auto-antigen AQP4 is expressed on the astrocytic foot processes suggesting a role for astrocytes in the pathogenesis of the disease. However, the astrocytes might play a more active role than has previously been suggested in the immune cascade of NMO pathology. Here we will review epidemiological, clinical diagnostic and therapeutic aspects of NMO and highlight the possible role of astrocytes as major direct and indirect players in the pathogenesis of NMO and related CNS inflammatory diseases.