NMO – A Sister to MS

Could we have an MS Research breakthrough on our hands? Findings by Australian Researchers published late last year were the first to indicate that MS may have a different origin than originally thought; suggesting that MS may not be a myelin disease.

Prof John Prineas and Dr John Parratt from the University of Sydney have been studying a subtype of MS called neuromyelitis optica (NMO), which is the most common form of MS in Asian populations. NMO primarily affects the optic nerve and spinal cord.

The average age of onset is about 40 years (10 years later than MS), but NMO can affect patients from 3 to 90 years old. Since NMO is more common in Asian populations than in the Western world, it was first called Asian opticospinal MS. The symptoms of NMO and MS are similar, but attacks of optic neuritis and myelitis in NMO are usually more frequent and more severe than those in MS. Standard MS treatments (e.g. interferons) are not only ineffective for NMO, but may even worsen the condition.

A reliable biomarker that distinguishes NMO from classical MS is the presence of NMO-immunoglobulin G (NMO-IgG) antibodies in the blood of NMO patients. NMO-IgG binds to aquaporin-4 (AQP4), a water channel protein in supporting cells of the central nervous system called astrocytes. It is suspected that damage to these supporting cells might cause a secondary loss of oligodendrocytes, the cells that produce myelin.

Dr Parratt examined autopsy tissue from 14 patients with NMO and 31 patients with MS and found that the mechanism of demyelination in early lesions of NMO was the same as that in MS. In NMO however, demyelination occurs several days or weeks after an initial loss of astrocytes around blood vessels. Astrocyte damage was also detected in some MS lesions. “Consequently, MS may not be a disease primarily of myelin but caused by the breakdown of astrocytes – a new breakthrough in MS research.” says Dr Parratt.

A national NMO database is now being established in Australia and we urge patients diagnosed with NMO as well as MS to register with the MSRA Brain Bank. Please call 1300 672 265 for more information.

Reference

Parratt J DE and Prineas JW (2010) Neuromyelitis optica: a demyelinating disease characterized by acute destruction and regeneration of perivascular astrocytes. Multiple Sclerosis 16(10) 1156–1172