However, as AQP4-Ab were discovered only a few years ago, many previous studies investigating the clinical and paraclinical features associated with myelitis and optic neuritis in patients with NMOSD either did not determine AQP4-Ab at all [1,26], or did not stratify patients according to their AQP4-Ab serostatus [27,28], or were based on relatively small patient numbers [24,25,28-34]. This evidence concerns the gene AQP4 and optic neuritis.