AQP4 and neuromyelitis optica: Patients with MOGAD usually have clinical phenotypes that demonstrate some overlap among several CNS acquired demyelinating syndromes, such as acute disseminated encephalomyelitis (ADEM), optic neuritis (ON), myelitis, encephalitis, aquaporin-4 (AQP4) Ab-negative neuromyelitis optica spectrum disorder (NMOSD), and others [5, 6].