In my last post, I stated that polymyalgia rheumatica (PMR) is a type of rheumatoid arthritis.
A couple of RheumaBlog’s readers gently questioned this assertion. Since the last thing I want to do is mislead anyone, I decided to dig into the subject more deeply. Is PMR a type of RA, as I asserted so blithely, backed by the Healthline article I linked to?
Well, um, no. It isn’t.
Here’s what I found out: PMR is a connective tissue disorder, an inflammatory condition that causes painful aching and stiffness in the muscles of the neck and shoulders, the lower back and the upper thighs. Sometimes the aching affects the hands and wrists. PMR can be chronic. It afflicts people aged 50 and older, a few more women than men.
According to Wikipedia, “The pain and stiffness [of PMR] result from the activity of inflammatory cells and proteins that are normally a part of the body’s disease-fighting immune system, and the inflammatory activity seems to be concentrated in tissues surrounding the affected joints.”
Polymyalgia rheumatica can come on quickly. While the pain can be quite intense and disabling, like RA it tends to be worst in the morning and often lessens as the day progresses. Periods of inactivity, such as sitting for more than 20-30 minutes, can aggravate it.
PMR is often associated with a kind of vasculitis (inflammation of the blood vessels) called giant cell arteritis. Some researchers believe PMR’s muscle pain might actually be referred pain from inflammation in the joints, ligaments and bursae of the shoulders and hips.
The American College of Rheumatology’s information sheet on PMR states that non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen “are not effective” in treating PMR. Instead, low-dose corticosteroids, such as prednisone, are generally prescribed. Because PMR can be chronic, patients sometimes need to stay on corticosteroids to keep the condition under control.
The information I found seems pretty clear: polymyalgia rheumatica is not a type of rheumatoid arthritis. But just to make sure, I emailed Dr. Irwin Lim, a rheumatologist and the director of BJC Health in Sydney, Australia. He writes an excellent blog for BJC that’s chock full of information about RA and other autoimmune diseases.
I asked Dr. Lim if polymyalgia rheumatica is a “type” of RA. His response (thanks, Dr. Lim!):
Polymyalgia Rheumatica is a different disease. It is not a type of rheumatoid arthritis.
PMR is related to a vasculitis called Giant Cell Arteritis. It is a steroid-responsive condition and sometimes DMARDs like Methotrexate are used to reduce the reliance on steroid.
However, rheumatoid arthritis can sometimes mimic PMR. In fact, all connective tissue diseases, if they cause large joint involvement limited to shoulder and pelvic girdle, may look like PMR. So it’s something Rheumatologists are aware of when treating PMR and I routinely measure rheumatoid serology.
However, true PMR is different from RA with a polymyalgic-type onset (i.e. mimicking PMR).
Read the American College of Rheumatology’s info sheet on PMR.
My apologies for publishing erroneous information about polymyalgia rheumatica—and thanks to RheumaBlog’s readers who caught the mistake.