Multiple sclerosis (experimental autoimmune encephalomyelitis)
Multiple sclerosis is a chronic autoimmune disease affecting the central nervous system, including the brain and spinal cord. The disease affects about 350,000 Americans and about 1.1 million worldwide. Age of onset is typically twenty to forty years old, women are affected more frequently than men (2:1 ratio), and it is most often prevalent in individuals of northern European ancestry. It is thought to be mediated primarily by a T-cell-mediated attack on the myelin sheats of certain nerve fibers, resulting in inflammation, demyelination, and gliosis (scarring). In addition, autoantibodies against components of myelin such as myelin oligodendtocyte glycoprotein (MOG) may be seen and also may contribute to disease pathogenesis by fixing complement. During the course of disease, the lesions classically occur at different times and in different locations. Symptoms include sensory loss, paresthesias (numbness, tingling), visual changes due to optic neuritis, tremor, ataxia, weakness, spasticity, and other neurological symptoms. Patients with multiple sclerosis can exhibit either a relapsing-remitting or a progressive course.