• NEUROIMMUNOLOGY
• MULTIPLE SCLEROSIS
• MYELIN

The clinical landscape of central nervous system (CNS) demyelination has changed significantly since 2003. A young woman presenting with optic neuritis, brainstem involvement, a severe long spinal cord syndrome and minimal cerebral involvement would undergo a dutiful but likely fruitless search for multiple sclerosis (MS) mimics such as sarcoidosis, systemic lupus erythematosus and Behçet’s disease. After obtaining a history devoid of connective tissue features, inconsequential blood and cerebrospinal fluid work-up and normal chest X-ray, the primary diagnosis nowadays would be neuromyelitis optica but historically atypical MS would have been a reasonable alternative. Although neuromyelitis optica was first described as far back as 1894, no biomarker distinguished it from MS, and furthermore for many years, there was a view that this disease was simply a severe variant of MS.1 MS remains the most common cause of non-traumatic disability in young people, and atypical forms of common diseases are far more likely than the zebras we worry about missing in the clinic room.2

Ironically it was the very discovery of a ‘zebra’ or rather aquaporin-4 antibodies (AQP4-IgG) in neuromyelitis optica spectrum disorder (NMOSD) in 2004 that provided validity to NMOSD being considered a separate nosological entity with a different pathogenesis, and ushered in a renewed appreciation of non-MS CNS inflammation.3 This discovery also shed light on the importance of astrocytes and antibody-mediated mechanisms in inflammatory CNS white matter diseases. With a reliable biomarker to identify NMOSD patients, it quickly became clear that there were important clinical, therapeutic and prognostic differences from MS. These findings emboldened further research into non-MS CNS inflammation, and in 2007, antibodies …