Regarding the DNA variants in the AQP4 gene, and in contrast with a study of Japanese patients which sequenced exons of the AQP4 gene and did not find any variant in 16 Japanese patients (13 sporadic cases, and 3 familial cases from 2 families) diagnosed with anti-AQP4 IgG positive NMO [20], we have found five DNA variants in Spanish NMOsd patients. This evidence concerns the gene AQP4 and neuromyelitis optica.