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Researchers Discover Specific Marker For Disease Misdiagnosed As MS
February 4, 2005

Researchers have discovered a specific antibody in the blood of individuals with a relatively rare disorder called neuromyelitis optica (NMO, also known as Devic’s syndrome) that clearly distinguishes it from multiple sclerosis. NMO was until recently regarded as a severe form of MS. Vanda A. Lennon, MD, PhD, Thomas Kryzer, and colleagues from the Mayo Clinic (Rochester, MN, and Scottsdale, AZ) and from the Tohoku University School of Medicine in Sendai, Japan, recently reported their findings in The Lancet (2004 Dec 11; 364[9451]:2106-12). This study was funded in part by the National MS Society.

The symptoms of NMO are restricted to the optic (eye) nerves and spinal cord. Recurrent episodes of inflammation that damage both the myelin that insulates nerve fibers and the nerve cells themselves result in severe symptoms, such as blindness and varying degrees of weakness or paralysis in the legs or arms. Full-blown NMO can be distinguished from MS using a combination of clinical, imaging, and spinal fluid tests. However, the initial symptoms of NMO are commonly mistaken for an attack of MS. Because MS and NMO have different treatment regimens, it is anticipated that a test which distinguishes these disorders at the onset of symptoms would improve treatment outcomes.

Through a series of laboratory studies Dr. Lennon and colleagues identified an autoantibody (a protein produced by the immune system that mistakenly attacks the body itself) that is specifically present in the blood serum of many individuals with NMO. This autoantibody (which the investigators named “NMO-IgG”) attaches to discrete regions of brain and spinal cord tissues obtained from normal mice. To determine how specific NMO-IgG is to NMO, the investigators examined specimens of blood serum from 124 people with NMO, and 75 people with MS and other neurological disorders. All of the serum specimens were masked so that investigators did not know in advance the clinical characteristics of the individuals sampled. They found the NMO-IgG autoantibody in nearly three-quarters of people with NMO, in nearly one-half of people whose symptoms were classified as being at high risk for developing NMO, and in none of those diagnosed with MS or other neurological or autoimmune disorders. The results suggest that this NMO-specific “marker” is sufficiently powerful to aid the diagnosis of NMO in people whose symptoms may indicate either NMO or MS.

Clinicians can request the blood test for NMO-IgG from Mayo Medical Laboratories. A positive result can help a neurologist to identify people at risk for NMO early in the course of the disease, allowing appropriate treatment to be initiated early and hopefully reduce the damage caused by this disease. The test may also be used to track response to treatment.

-- Research Programs Department