Rituximab works by killing B lymphocytes in the body. It was originally used to treat lymphoma. New research has shown that abnormal B lymphocyte function is an important cause of the development of optic neuromyelitis optica. The application of rituximab to kill B lymphocytes, i.e., to remove most of the disease-causing B lymphocytes, can lead to remission of clinical symptoms and a reduction in the number of attacks in patients. Currently, rituximab is used in patients who have frequent attacks and for whom hormones or other traditional immunosuppressive drugs are not effective.