More than 90% of NMO-related LETM patients develop a relapsing–remitting course, accumulating disability; relapse rate is related to the extent of the spinal cord lesion and the presence of AQP4-IgG, but not its titer.3 The diverse courses of NMO observed during longitudinal studies led to the broadening of the diagnostic criteria for NMO spectrum disorders (NMOSD). Here, AQP4 is linked to neuromyelitis optica.