Low sensitivity of anti-aquaporin-4 antibody in multiple sclerosis, longitudinally extensive spinal cord lesions and neuromyelitis optica in Australians

Background and Objective: Multiple Sclerosis (MS) is the most common neurological disease of young adults in Western countries. The spectrum of demyelinating disease in Western countries is characterised by predominance of conventional MS and small proportion of neuromyelitis optica (NMO). NMO is similar to optic-spinal MS reported in Asia in many aspects. It has been argued that relapsing NMO and optic-spinal MS is different from conventional MS with clinical and laboratory features such as female predominance, low frequencies of oligoclonal IgG bands, longitudinally extensive (>3 vertebral segments) spinal cord lesions (LESCLs), CSF pleocytosis, and poor clinical prognosis. Moreover, a recently identified serum autoantibody, so called NMO-IgG, has been proposed as a biomarker to distinguish NMO from conventional MS. The target antigen of NMO-IgG was identified as aquaporin-4 (AQP4) water channel protein.1 An anti-AQP4 antibody assay using human AQP4-transfected cells appeared more sensitive than the original NMO-IgG assay.2 The presence of anti-AQP4 antibody seemed to be associated with LESCLs and exacerbation of disease.3 Our study aimed to investigate the prevalence of anti-AQP4 antibody in conventional MS, NMO and LESCL patients from a Western Australian MS cohort.