What Is Neuromyelitis Optica?
Neuromyelitis Optica (NMO), or neuromyelitis optica spectrum disorder (NMOSD) aka Devic’s Disease (named after the doctor who initially discovered it), is a rare neurological autoimmune disease- meaning the body’s own immune cells begin to attack components of the nervous system, predominantly the optic nerve and spinal cord. NMOSD can also target areas of the brain. Historically, NMO has been misdiagnosed with multiple sclerosis (MS), another autoimmune disease of the central nervous system (CNS). Misdiagnosis can lead to either delay of appropriate treatment for NMO or inappropriate treatment, which can potentially exacerbate the disease.
NMO patients experience optic neuritis (causing eye pain and vision loss), transverse myelitis (leading to limb weakness and paralysis), as well as decreased sensation and loss of bladder and bowel control. Other symptoms can include intractable hiccuping, nausea and vomiting, sexual dysfunction, neuropathic pain, spasticity and chronic fatigue.
Mechanism of Disease
NMOSD is a distinct disease from multiple sclerosis (MS), typically sparing the brain and affecting a higher proportion of females to males (4:1). NMO can specifically lead to the formation of pathogenic (disease-causing) antibodies against aquaporin 4 (AQP4), or NMO-IgG, in the vast majority of patients, which is believed to be a mediator in spinal cord destruction. While nearly 80% of NMO subjects have these antibodies, NMO patients without NMO-IgG have similar spinal inflammation and destruction. Further diverging from MS, in which patients most often have mild attacks with good recovery, NMO attacks lead to severe disability, most often with incomplete recovery. Other subtypes of NMOSD can include MOG-seropositivity. MOG is protein that helps make up the CNS, and antibody formation against this protein can cause damage. Data show that patients can be either AQP4-IgG or MOG-IgG positive, but not both.
Common treatments for acute relapse include high dose intravenouse (IV) steroids, IV immunoglobulin (IVIG), and/or plasmapheresis. (See table below).
To Reduce/Prevent Relapse
Although there are currently no FDA-approved treatments or cure for NMO, a number of immunosuppressive therapies have been used to help reduce relapse. Because NMO is a rare disease, affecting about 15,000 in the United States, it has been granted Orphan status. An Orphan disease is one that affects less than 200,000 in the United States. For the NMO population, orphan drug designation has been granted to a number of immunosuppressive therapies. (See table below).