Anti-aquaporin 4 antibody in Japanese multiple sclerosis: the presence of optic-spinal multiple sclerosis without long spinal cord lesions and anti-aquaporin 4 antibody

Background: Anti- aquaporin 4 ( AQP4) antibodies were found in patients with neuromyelitis optica ( NMO) and Japanese optic - spinal multiple sclerosis ( OSMS). Objective: To review the clinical features and investigate antiAQP4 antibodies of Japanese patients with multiple sclerosis ( MS), with or without long spinal cord lesions ( LCL). Methods: Anti- AQP4 antibodies were examined in the sera of 128 consecutive Japanese patients by the immunofluorescence method using AQP4 transfected cells. Results: The 45 LCL- MS patients included 28 with a long spinal cord lesion extending contiguously over three vertebral segments on sagittal T2 weighted images ( long T2 lesion) and 17 with segmental cord atrophy extending more than three vertebral segments. We identified 25 patients with anti- AQP4 antibody with LCL and anti- AQP4 antibody. Anti- AQP4 antibody was found in 12/ 17 ( 70.6%) LCL- MS patients with segmental cord atrophy, and in 13/ 28 ( 46.4%) LCL- MS patients without segmental long cord atrophy ( p = 0.135, Fisher's exact test). Seropositive MS patients with LCL had more relapses than seronegative patients ( p = 0.0004, Mann Whitney U test). 9 patients with OSMS were negative for antiAQP4 antibody who did not show LCL. Conclusion: These results suggest that an anti- AQP4 antibody is found not only in MS patients with long T2 lesions but also in patients with segmental cord atrophy extending more than three vertebral segments. It is a marker of LCL- MS showing frequent exacerbations. Japanese OSMS cases comprised those that were identical to NMO cases and those that were more closely related to classic MS.