With the detection of AQP4 antibodies, the clinical spectrum of NMO has broadened, and currently also AQP4-positive longitudinally extensive transverse myelitis (LETM) and AQP4-positive recurrent optic neuritis are regarded as part of NMO spectrum disorders (NMOSDs) [1, 6]. Here, AQP4 is linked to neuromyelitis optica.