Neuromyelitis optica spectrum disorder (NMOSD) or Devic disease is a chronic condition affecting the brain and spinal cord. The condition is characterised by inflammation of the optic nerve (optic neuritis) and spinal cord (myelitis). While once thought to be a single, non-recurring episode of inflammation, it is now understood that most NMOSD patients experience repeated attacks separated by remission periods, which can vary from weeks to years. In its early stages, NMOSD can be mistaken for multiple sclerosis (MS) due to overlapping symptoms.
Source: https://rarediseases.org/rare-diseases/neuromyelitis-optica/
