Multiple sclerosis (MS) is one of the most common diseases of the central nervous system (brain and spinal cord). Today more than 2.8 million people around the world have MS. MS is an inflammatory demyelinating condition. Multiple sclerosis (MS) is an autoimmune disease in which the immune system attacks myelin, the insulating cover of nerve cells, causing damage to the central nervous system. This impairs the nervous system's ability to transmit signals. Multiple sclerosis (MS) is an autoimmune condition that affects your brain and spinal cord (central nervous system). Policy. With MS, your immune system mistakenly attacks myelin cells. These are the protective covers (sheaths) that surround your brain and spinal cord nerves. MS symptoms usually begin in young adults, between ages 20 and 40. MS affects people differently. A small number of people with MS will have mild symptoms with little disability, but others will experience worsening symptoms that will lead to increased disability over time. Multiple Sclerosis, or MS, is a complex disease that affects countless individuals around the world. Learn what causes MS, the different types of MS, and more. People with multiple sclerosis (MS) tend to have their first symptoms between the ages of 20 and 40. Early on, the symptoms get better, but then they come back. This is called relapsing-remitting. Multiple sclerosis is a disorder in which the body's immune system attacks the protective covering of the nerve cells in the brain, optic nerve and spinal cord, called the myelin sheath. And this sheath is often compared to the insulation on an electrical wire. Like many diseases, multiple sclerosis (MS) affects everyone differently, bringing symptoms that can range from mild to severe. This autoimmune condition affects your central nervous system, causing issues like muscle weakness, vision changes, numbness and memory issues. Multiple sclerosis is a chronic nervous system disorder. In MS, the immune system attacks the fatty substance that surrounds and protects nerves (myelin). Over time, the myelin breakdown can lead to scar tissue buildup (sclerosis). When this occurs, the nerves have trouble sending electrical signals to the brain as they should. MS is a chronic, or long-lasting, disease that can affect your brain, spinal cord, and the optic nerves in your eyes. It can cause problems with vision, balance, muscle control, and other basic.