OCD will not kill you. However, it is possible to die as a result of doing a ritual.
For example, if every time you hit a bump while driving you look in the rearview mirror to see if you hit someone, it’s possible that your distraction in looking for a body could lead to your getting into an accident.
If you are a hoarder, and your house if full of papers and other items, and there is a fire, it may be almost impossible for you to get out because of the amount of fuel for the fire and the likely rapidity with which the fire will spread.
Or if you are a washer, you could possibly do so much damage to your skin that you get some serious infections that could make their way into your bloodstream and lead to your death.
While these are all rare occurrences, they are possible, and could be the result of doing rituals.