Have you had a myomarker panel? The rash on the chest may be a “shawl sign” which coupled with the muscle weakness may indicate some form of myositis overlap syndrome. It’s often connected to Raynaud’s.

I have dermatomyositis that started out with all over muscle pain, on and off positive ANA, one positive RNP, and then came the muscle weakness and rash on the chest.

My rheumatologist kept throwing a myomarker into my labs and I probably did 7 or 8 that came back negative before I started to test positive. Just a thought. Good luck!