context: Multiple sclerosis ( MS) and amyotrophic lateral sclerosis ( ALS) are different diseases with some similar features and symptoms. They both: Affect your muscles and your ability to move your body Attack your brain and spinal cord Have âsclerosisâ in their name Cause scarring or hardening around nerve cells They have some key differences, though. MS is an autoimmune disease that causes your body to attack itself. ALS, also called Lou Gehrig's disease, is a nervous system disorder that wears away nerve cells in your brain and spinal cord. Both are treated differently. " Sclerosisâ comes the Greek word for âscar.â Both ALS and MS cause scarring of the covering of nerve fibers. But the process of how that happens is different for each. Nerve cells in your body are wrapped in thin coverings called myelin sheaths. They protect these cells, similar to how insulation protects electrical wires. When you have MS, your body attacks the myelin sheaths in your brain and spinal cord. When myelin sheaths are damaged, signals from your brain to other parts of your body get short-circuited. ALS breaks down the actual nerve cells in your brain and spinal cord. These cells, called motor neurons, are in charge of the voluntary muscles in your arms, legs, and face. You lose control of your motor functions, and as the motor neurons break down, the myelin sheaths harden. In its early stages, some of the symptoms of ALS can be similar to those of MS. These include: Stiff, weak muscles Twitching or spasms Fatigue Trouble walking If you're having these symptoms, don't try to guess what's going on. See a doctor and get a diagnosis. As ALS attacks the nerves that deal with movement, your symptoms will get worse. In the later stages of the disease, you can have: Slurred speech Shortness of breath Trouble breathing Trouble swallowing An inability to move (paralysis) Most people with ALS live 5 years or less after their diagnosis, but some live much longer. Research is underway to find treatments to extend and improve the quality of life. With MS, the course of the disease is harder to predict. Your symptoms may come and go, and may even disappear for months or years at a time. Unlike ALS, which affects only nerves involved in movement, MS can also affect your: Senses -- taste, smell, touch, sight Bladder control Mental and emotional health Sensitivity to temperature Because of complications related to the disease, the life expectancy of someone with MS is about 7 years less than someone without it, research suggests. MS is diagnosed earlier in life than ALS. It's usually discovered between the ages of 20 and 40. ALS is often diagnosed between 40 and 70. They affect genders differently. More women than men get MS. ALS is more common in men. MS is most common in Caucasians. ALS affects all ethnic groups equally. ALS can be inherited, but MS can't. Up to 10% of ALS cases are passed down directly through genes. That's not so with multiple sclerosis. But if your mom, dad, or sibling has MS, you're at a higher risk of getting the disease. More people in the United States have MS than ALS. An estimated 12,000-30,000 people have ALS nationwide. More than 400,000 are living with MS. There's no cure for either condition, but treatments can help slow both diseases. Lifestyle changes can help you manage your symptoms and improve your quality of life, too.