According to several studies, the occurrence of optic neuritis and/or transverse myelitis in AQP4-IgG seropositive patients with systemic autoimmune disease (e.g., SS or SLE) should not be regarded as a vasculitic complication of a systemic disorder, but as the coexistence of these two diseases [2,63]. The gene discussed is AQP4; the disease is optic neuritis.