Update on epidemiology and treatment of NMOSD

Neuromyelitis optica (NMO) spectrum disorders (SDs) considered under the umbrella term “Autoimmune Aquaporin-4 Channelopathy” represent an evolving spectrum of CNS-inflammatory-autoimmune-demyelinating diseases for which a specific antigen has been identified-the astrocytic water channel aquaporin-4 (AQP4). MS lacks a distinguishing biomarker. The discovery of AQP4-IgG represents a significant shift from emphasis on the oligodendrocyte and myelin to the astrocyte. The NMO of today represents a relapsing spectrum of disease, extending beyond the optic nerves and spinal cord to include brain (especially in children) and rarely muscle. Most patients have MRI brain abnormalities and these are consistent with MS in up to 10% of patients. Women are affected more commonly than men (ratio 9:1). For 1 in 5 patients, initial onset occurs in childhood or in senescence. Asian and African-American populations are disproportionately affected. By contrast, among white populations MS is about 40 times more common than NMO. A recent Mayo Clinic collaborative study with Dr Philippe Cabre from Martinique compared the incidence and prevalence of NMOSD in 2 ethnically diverse populations (Martinique vs Olmsted County, USA). This study reported a higher age and sex adjusted incidence (7.3 vs 0.7/1,000,000 person-years [p<0.01]) and prevalence (10 vs 3.9/100,000[p=0.01]) among Afrocaribbeans compared with Caucasians. Improved understanding of the molecular pathogenesis has identified novel targets that hold promise for potential monotherapies or as a multi-faceted combined therapeutic approach. Some of these are anticipated to improve the outcome for patients with AQP4 channelopathy. Randomized clinical trials are currently assessing the efficacy and safety of newer immunotherapies.