MCTD will eventually kill you, unless you are of the view that only develop subcotaneous symptons.
Also most common complication leading to death is not "hypertension muscle" (what ever that is supposed to mean), it's PULMONARY HYPERTENSION.
I have MCTD and my doctors have very well explained that only the medication you need to stop your immune system from attacking your body will shorten your life, not to mention the different types of complications and of course the fact that all organs can be involved. heart, kidneys, liver, spleen, skin, brain just about everything.