Can i die from myositis if i ignore it?

No: Myositis itself does not kill provided heart muscles are not affected. Patients die from complications from myosotis like heart, lung, infraction etc.

You typically don't die, but myositis can worsen causing great harm. The longer you wait for treatment of the muscle inflammation, the more damage to the muscle. Also, the lungs can be affected and the damage may be irreversible. Myositis requires prompt investigation as to the cause. Myositis can be mild to severe.