AQP4 and optic neuritis: AQP4 antibodies were present (i.e., Ab-ratio > 11) in 21/37 patients with NMO and in 6/6 of those with LETM, but in only 5/291 control samples, including 4/144 with MS and 1/73 with other neurological diseases, 0/45 with rheumatological diseases, and 0/29 healthy individuals (Fisher exact test, Chi-square values ranging from 11.099 [NMO group versus optic neuritis/optic neuropathy group, p = 0.001] to 49.353 [NMO versus MS with optic neuritis group], p < 0.001 for all other tests) (Figure 2; Table 1).