AQP4 and neuromyelitis optica: Our results found that 100 % of the anti-AQP4 (+) ABS patients experience clinical relapse, and 71.43 % of anti-AQP4 (+) ABS patients convert to NMO in the following 3 years, while only 11.76 % of the anti-AQP4 (-) ABS patients convert to NMO, and the cumulative NMO conversion probability is significantly higher in anti-AQP4 (+) ABS patients than that in anti-AQP4 (-) ABS patients.