視神経脊髄型多発性硬化症における抗aquaporin-4抗体の診断的意義

Anti-aquaporin-4 antibody in opticospinal multiple sclerosis

脊髄に長大病変（LCL）を有する視神経脊髄型多発性硬化症（OSMS）は，neuromyelitis optica（NMO）との異同が論議される病型である。OSMS-LCLについて，抗aquaporin-4抗体を解析したところ，NMOで報告されたNMO-IgGと同様の頻度で陽性であり，本邦OSMSにも欧米のNMOと同一病態機序による一群が存在することが確認された。Aquaporin-4はastrocyteのendfeetに発現する水チャネル分子であり，OSMS-LCLの広汎な浮腫を伴う炎症性病変との関連が考えられている。

NMO-IgG, which binds to aquaporin 4（AQP4）, is a specific marker of neuromyelitis optica（NMO）. Because the Japanese opticospinal multiple sclerosis（OSMS）has very similar clinicopathological features to NMO, we established an immunohistochemical detection system for the anti-AQP4 antibody using AQP4-transfected HEK cells to clarify that NMO and OSMS have the same entity. Approximately 60％ of the patients with OSMS with long spinal lesions（LCL）, usually showing severe paraparesis with blindness, were positive for this antibody；those with OSMS without LCL or those with a conventional form of MS were negative. The frequency of anti-AQP4 antibody in OSMS-LCL was similar with those of NMO-IgG in NMO reported by Lennon et al. The role of anti-AQP4 antibody on the lesion development in OSMS or the reason for preferential involvement of optic nerve and spinal cord in OSMS is not yet elucidated.