Neural Regen Res. 2016 Mar;11(3):410-1. doi: 10.4103/1673-5374.179048.
Hiroaki Yokote and Hidehiro Mizusawa, M.D., Ph.D.*
Neuromyelitis optica spectrum disorder (NMOSD) is a chronic inflammatory disorder of the central nervous system that particularly involves the optic nerve and spinal cord. It is pathologically characterized by astrocytopathy, followed by tissue destruction (Fujihara, 2011). Historically, NMOSD has been considered to be an Asian optic-spinal form of multiple sclerosis (MS), as patients with NMOSD were distributed predominantly in Asian rather than in Western countries.
Highly sensitive and specific NMO-specific immunoglobulins (NMO-IgGs) that target aquaporin 4 (AQP4) have been discovered in patients with NMOSD. This led to NMOSD being considered as a separate clinical entity from MS. Moreover, the finding that interferon (IFN)-β, widely used and proven effective in patients with MS, sometimes exacerbates NMOSD (Papadopoulos et al. 2014), further led to this distinction. Additionally, new generation drugs including fingolimod and natalizumab are also known to exacerbate NMOSD (Papadopoulos et al. 2014), suggesting that the distinction between MS and NMOSD is critical in determining appropriate therapy.
Although MS and NMOSD are essentially distinct diseases, recent studies have shown similarities. To reduce the misdiagnosis, it is crucial to know not only the differences but also the similarities between these two diseases. In this article, we focus on the similarities between MS and NMOSD and discuss the association between these overlaps and disease pathogenesis, from pathological, radiological, and immunological perspectives.
Pathological characteristics of MS and NMOSD: The characteristics of MS lesions have been well defined, and although heterogeneous, they can be classified into 4 types (Lucchinetti et al. 2001): Pattern I and II lesions are characterized by active demyelination, associated with a T cell- and macrophage-dominated inflammation. The distinguishing feature of pattern II lesions is the prominent deposition of Igs and complements. Pattern III shows diffusely spread demyelination with prominent loss of myelin-associated glycoprotein in association with oligodendrocyte apoptosis. Pattern IV lesions also present with demyelination, accompanied by oligodendrocyte death. Thus, demyelination is a key feature of MS lesions.
On the other hand, NMOSD lesions classically present with complement deposition, granulocyte infiltration, and astrocyte necrosis, which lead to global tissue destruction (Fujihara, 2011). However, Misu et al. (2013) described that NMOSD lesions are highly heterogeneous and can be categorized into 6 different types according to pathological analyses. Lesions of type 1, 2, and 3 reflect the typical NMOSD lesions described previously. These lesions are followed by demyelination, leading to global tissue destruction, accompanied by Wallerian degeneration. Type 4 and 5 lesions are characterized by clasmatodendrosis of astrocytes, in the absence of complement activation. Interestingly, type 6 lesions are characterized by primary demyelination in association with oligodendrocyte apoptosis and astrocytic clasmatodendrosis, which is similar to a pattern III lesion in patients with MS. Moreover, the authors observed that type 6 lesions were seen in 4 of 7 patients with NMOSD, suggesting that type 6 lesions are common in patients with NMOSD.
Continued at source.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4828999/