Multiple sclerosis (MS) is a central nervous system disorder. This means it affects the brain and spinal cord. It is an autoimmune disease as it is inflammatory—meaning that white blood cells, which protect against infection, enter the nervous system and cause damage. The harm is done because the myelin sheath, the protective coating for nerves, is stripped off by the antibodies produced by the immune system. (This is called demyelination.) MS is a long-term disease that can happen to anyone. Pediatric MS is multiple sclerosis that begins in children or teens. About 98% have relapsing-remitting MS, versus 84% of adults with MS. This means that symptoms come and go (relapse and remit). When symptoms are gone, the disease is still able to progress. This condition may also be called pediatric-onset multiple sclerosis (POMS), early-onset MS, or juvenile MS. Relapses seem to happen more often in children and teens. This group appears to recover from the neurologic disability more quickly but are at increased risk of cognitive difficulties that can affect school work. There are about 730,000 people in the U.S. with multiple sclerosis. Onset during childhood accounts for about 5% of the total. Before puberty, the ratio of females to males who develop pediatric MS is about equal. After puberty, the ratio is about 2-3 to 1. This might indicate that sex hormones have a role in developing the condition.