Given that AQP4-IgG-positive NMO has been demonstrated to be frequently associated with connective tissue disorders such as systemic lupus erythematosus, Sjögren’s syndrome, or rheumatoid arthritis in a substantial number of cases [1, 59, 229], the latter fact does not argue against but rather supports a diagnosis of NMO. This evidence concerns the gene AQP4 and neuromyelitis optica.