Although it was reported that positivity for antibodies to AQP4 and evidence of LESCLs distinguish NMO from MS with 76% and 98% sensitivity, respectively [22], 4/68 (5.9%) patients in this extension study, which excluded individuals with LESCLs, were anti-AQP4 antibody-positive. The gene discussed is AQP4; the disease is neuromyelitis optica.