@jfannarbor

PMR is no different than other autoimmune disorders that don't have definitive diagnostic tests. There are some characteristic symptoms of PMR but these symptoms overlap with other inflammatory conditions so they aren't specific to PMR either.

ESR and CRP are nonspecific tests for inflammation and they might be elevated for almost any reason. A rapid response to prednisone is a characteristic of PMR but many other inflammatory conditions and types of arthritis respond in the same way. When a synthetic corticosteroid was first tried for RA ... people were "miraculously cured."

The following little abstract says it all about the miracle of corticosteroids. What is often overlooked is the last little phrase that says, "the side effects are still daunting."
https://pubmed.ncbi.nlm.nih.gov/26611547/
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I remember when I was first diagnosed with PMR. I was fortunate to have the same rheumatologist for 15 years after being diagnosed with PMR. We could be brutally honest with each other. I remember when I somewhat accused her of only diagnosing me with PMR because I wanted prednisone. It was true that I wanted prednisone but not for PMR because I didn't know there was something called PMR. I respected her because we shared the same goal of getting me off prednisone.

The only reason there were three rheumatologists in the room when PMR was diagnosed was because nobody was sure what was wrong with me. They were reluctant to prescribe prednisone to me because I already had a diagnosis of reactive arthritis which isn't treated with long term prednisone. I didn't understand why reactive arthritis wasn't treated with prednisone since I had been taking prednisone for many years already. My flares of reactive arthritis usually happened with a flare of uveitis so my ophthalmologist prescribed all the prednisone to me.

PMR was diagnosed because I told the rheumatolgists that the pain gets really bad if I don't take prednisone. Everything else was ruled out when they asked me if the pain was anything like what I ever had experienced before. When I said the pain was completely different then that confirmed PMR.

I really liked my first rheumatologist that I had for many years. However, I needed a different rheumatologist when I retired and transferred my care to the VA. The next rheumatologist wasn't sure about PMR but wanted me to try something new because it might be "my best chance of ever getting off prednisone." I was told there was new research about a biologic being used for GCA. I didn't have GCA but was told that the biologic should work for PMR if I was willing to try it. You probably know what happened when I tried Actemra.

I think a bigger problem nowadays is that not enough patients are willing to try other treatment options for PMR. There is the widespread belief that prednsisone is the "only option" for PMR. Another problem is how expensive it is to do research in order to get new treatments approved. There are some doctors who will say that prednisone wouldn't be FDA approved for PMR except that it was grandfathered in.