The few studies that reported antibody-specific incidences all found a much higher incidence of AQP4-IgG-positive than AQP4-IgG-negative NMOSD [156, 157, 190]; in line with this, AQP4-IgG-positive patients accounted for most cases of NMO or NMOSD in major cross-sectional studies. The gene discussed is AQP4; the disease is neuromyelitis optica.