I posted at some length on my experiences with PMR a while ago (Sorry, can't remember who it was in response to.)
Firstly, it is most certainly an auto-immune triggered condition.
Secondly, my experience might trigger extreme responses, depending on your mind-set, but all I know is, it worked for me, and yes, it is all in the mind (if you use that as a sceptical response) because of course it's all in the mind - in my opinion.
Once I actually made it to my GP, after about 4 months of increasingly excrutiating pain and immobility, it turned out that an emergency consultation with a rheumatologist was about another 4 months away!!
In the meantime, my yoga teacher, who had suffered a number of debilitating conditions in her journey back to good health in her (then) late 60s, recommended her kinesiologist. I didn't have the foggiest idea what a kinesiologist was, but her testimonies of health issues resolved after being written-off by conventional practitioners, convinced me.
She also recommended her nutritionalist, who in turn recommended a reflexologist. I saw all of them.
All three detected the same underlying issues. I am always very taciturn in such situations, because I am naturally suspicious of them building up to a diagnosis based on one's responses to open leading questions! Believe me, I give nothing away! I was therefore impressed and convinced.
Anyway, long story short (it's in that earlier post), by the time I saw the rheumatologist I knew I was feeling better than I had been, despite being told by the rheumatologist that was "impossible".
When the test results came back, she was visibly surprised that I needed a much lower dosage of steroids than she thought I would need! She qualified this by saying "Believe me, the doseage will go up, and continue to go up"
Well it didn't. It continued to go down. After 2 years I was off steroids altogether, despite having been told I would be on them for life!
I truly believe the mind is a great healer, and I subscribe to Reiki, and the power of universal energy in general.
I guess all I am saying is that there are alternative paths to healing, and if you believe in them, they work (of course) 