AQP4 and neuromyelitis optica: There seems to be no major clinical differences between the AQP4-Ab negative and positive relapsing groups.[1] In Japanese cases, the frequency and severity of relapses seem less in antibody-negative patients.[13] Only 12.5% of monophasic NMO patients are antibody positive, whereas 80% of patients with relapsing NMO are seropositive.