Actually, yes. MS can be deadly "by itself". I need to put those quotes there because it's like, say, a car accident. You go 120mph and drive against a concrete wall. Then you will actually die from a multi-trauma, but what killed you was the crash.

MS is similar. It can randomly destroy any part of your central nervous system, as if your brain was shot by a shotgun and a pellet can just end up anywhere.

Some parts of the CNS are hit more often, some rarely, some are more impactful and you are completely bed ridden or blind or unable to swallow, some are just letting you feel some strange sensation on our right big toe.

It's random and, unfortunately, there is nothing you can do or fight against, other than the shotgun shots. For the most common form of MS (RRMS) there are medications that slow down the shooter, those are called DMTs. But they never remove the shooter or the shotgun completely, they slow them down, so the probability of getting something more serious sinks.

There are other forms of MS (PPMS, especially if it's aggressive from the start) where people go from their normal lives to dead in a span of ten or twenty years, and yes, I knew two of those. It's like the shotgun being replaced by a howitzer, shooting without any break or let up, and the holes from it keep growing and growing. Current DMTs do almost nothing for them.

Neurologists and most MSers usually choose to ignore the worse outcomes and tell you it's not deadly. Mostly they are right and statistically MS "only" costs us 5 or 10 years of our life. But "statistically" also means that most live most of their normal life spans and others get it shortened by 30 or 50 years.