Sequential or concomitant attacks of transverse myelitis and optic neuritis, with contiguous spinal cord MRI lesions extending over three or more vertebral segments with the presence of anti-aquaporin 4 antibodies (AQ4 Ab) not only define NMOSD but also differentiate it from multiple sclerosis [3, 12]. The gene discussed is AQP4; the disease is transverse myelitis.