Your question is understandable. You may have heard of someone that died from MS, such as J. K. Rowlings mother. However, this is a very rare exception. J. K. Rowling herself talks about her mother having an unusually progressive form of the disease (which she refers to as galloping) and not receiving adequate medical care, due to financial constraints and other reasons.
Life expectancy of a person with MS is said to be normal, about 95% of the national average life expectancy of almost 80 years. However, even this slight reduction is based on combining all people with MS, which is misleading, as:
- It includes (and is affected) by very severe cases of MS, but not the very mild ones that go undiagnosed. A few patients with severe disability may die from complications of the disease, such as pneumonia, severe urinary tract infections or widespread skin breakdown (from bedsores). Even the majority of these few cases can be prevented with adequate medical care.
- This mostly reflects people that were not on disease-modifying treatment from an early point in their disease. These drugs just became available in the early 1990s. Advances in care for people with MS are steadily closing even the small gap in life expectancy.
Sources:
J.K. Rowling, I miss my mother so much - J.K. Rowling's narrative of her mother's battle with multiple sclerosis. Inside MS Summer 2002.
National Multiple Sclerosis Society, Prognosis
Carol Turkington, The A to Z of Multiple Sclerosis, Checkmark Books, 2005.

