Objective To analyse clinicoepidemiological features of neuromyelitis optica in a large cohort and to compare the differences between onset age, gender and clinical phenotypes. Methods Antiaquaporin-4 antibody (AQP4-ab) levels were tested in 2366 serum samples of patients diagnosed as having central nervous system inflammatory demyelinating disorders by their referring physicians. AQP4-ab was measured by indirect immunofluorescence staining using human AQP4-transfected HEK 293 cells. A blinded analysis was performed and was combined with clinical information. Results A total of 583 patients (91.4% women) were AQP4-ab-positive. The average onset age was 42.9615.9 years. According to MRI studies, spinal-cord lesions were detected in 85.3% of the patients, longitudinally extensive transverse myelitis in 72.7% and cerebral lesions in 51.1%. Unilateral or bilateral blindness was observed in 16.2% of patients, 19.8% were associated with Sjo Β¨gren syndrome, and 13.6% were associated with thyroid diseases. Myelin basic protein was detected in the cerebrospinal fluid of 57.5% patients. In addition, men presented with an older onset age, a greater number of brainstem MRI lesions and positive myelin basic protein in the cerebrospinal fluid. All child-onset patients (<15 years, nΒΌ9) presented with optic neuritis as the first symptom, while older-onset patients presented with myelitis. Twenty patients initially developed limited brain lesions, and seven of these patients did not develop optic or spinal lesions during the 1e5-year follow-up period. Conclusions The clinical characteristics of AQP4-abpositive patients were similar. However, optic neuritis was more common in paediatric patients, while myelitis was more common in older patients. A small number of patients exhibited only cerebral, brainstem, or cerebellar lesions during the initial several years and lower Extended Disability Status Scale scores.
Neuromyelitis optica (NMO) is an inflammatory demyelinating disease of the central nervous system that primarily affects the optic nerve and spinal cord with highly specific autoantibody NMO-IgG levels seen in the serum of NMO patients. 1 The target antigen of NMO-IgG has been identified as aquaporin-4 (AQP4), a water-channel protein predominantly expressed in the central nervous system. 1 2 NMO-IgG expression is restricted not only to typical NMO but also to NMO spectrum disorders (NMOsd) as well that include the following clinical features 3 : (1) limited disease forms, such as optic neuritis (ON) or longitudinally extensive transverse myelitis (LETM);
(2) atypical brain lesions with characteristics typical for NMO and positive NMO-IgG; and (3) ON or LETM associated with a systemic autoimmune disease.
An increasing number of studies have reported the clinicoepidemiological features of NMO, 4e9 although the patient number in each study has been insufficient. Therefore, the population prevalence of NMOsd has not yet been firmly established. The present study analysed clinical and epidemiological features in a large group of Japanese patients with NMO. Anti-AQP4 antibody (AQP4ab)-positive or AQP4-ab-negative patients who exhibited characteristic NMO clinical features were compared and analysed under identical conditions at a single institute using an antibody assay system.