Fibromyalgia & Polymyalgia Rheumatica: Know the Difference

Similar, but Not the Same

An elderly woman clutches her painful shoulder.
Jose Luis Pelaez Inc/Getty Images

We hear all the time that it's hard to diagnose fibromyalgia because it's similar to so many other conditions. One of those similar conditions is polymyalgia rheumatica (PMR).

It's possible that PMR could be misdiagnosed as fibromyalgia (or vice versa), or that it could be overlooked in people with fibromyalgia.

These two conditions, however, are very different and require different treatments. Knowing the symptoms of both can help you recognize whether you may have a new or undiagnosed condition that needs to be addressed.

What is Polymyalgia Rheumatica?

PMR is an inflammatory disease that's believed to be autoimmune. It's seen almost exclusively in people over 65. Doctors may not even consider it in anyone who's not a senior citizen.

Among people older than 50, about 0.5 percent have PMR, making it a rare disease. (To give you a comparison, fibromyalgia effects between 2 and 4 percent of the U.S. population.) A 2014 study (Haliloglu) suggested that PMR may be present in about 3 percent of people with fibromyalgia, which suggests that it's considerably more common in this group than in the general population.

PMR generally causes muscle pain and stiffness in specific parts of the body, including the:

  • Shoulders,
  • Neck,
  • Upper arms,
  • Hips,
  • Buttocks,
  • Thighs,
  • Sometimes the wrists, elbows, or knees.

The stiffness is almost always worst in the morning, when it can severely limit the ability to perform even basic tasks such as getting out of bed and getting dressed.

PMR can include other symptoms as well, such as:

  • Fatigue,
  • Low-grade fever,
  • Loss of appetite,
  • Malaise (a general feeling of unwellness,)
  • Depression.

When this disease strikes, symptoms generally come on quickly.

How are PMR & Fibromyalgia Different?

Let's look at the information above, point by point, to compare these two conditions.

  • PMR involves joint and muscle inflammation. Fibromyalgia may involve inflammation of the fascia (a thin layer of connective tissue that surrounds muscles and organs,) but it's a much lower-grade inflammation than that found in PMR.
  • PMR has features of an autoimmune disease. Fibromyalgia isn't currently classified as an autoimmune disease but there's some evidence that at least some subgroups may involve autoimmunity.
  • PMR is almost exclusively found in people over 65. Fibromyalgia is most common in women of childbearing age. (However, it's possible for anyone to develop either condition.)
  • PMR causes pain and stiffness in specific parts of the body. Fibromyalgia causes widespread pain. Some people may have specific pain patterns, but this varies greatly from one person to another.
  • PMR pain and stiffness are worst in the morning. Some, but not all, people with fibromyalgia may have specific symptoms that are more pronounced in the morning. However, many have their worst pain in the evening or at night.
  • PMR can include fatigue, low-grade fever, loss of appetite, malaise and depression. Fibromyalgia involves fatigue and may involve depression. Fever, loss of appetite and malaise are not considered fibromyalgia symptoms.
  • PMR generally comes on quickly. Some cases of fibromyalgia come on quickly while others involve a slow build-up of symptoms.

Diagnosing & Treating Polymyalgia Rheumatica

No single blood test can diagnose PMR. Doctors consider the full range of symptoms along with a lab test called the sedimentation (or "sed") rate. An elvevated sed rate is an indicator of inflammation. (In people with fibromyalgia, the sed rate is typically normal or slightly elevated.)

PMR is generally treated with steroids and can often be well controlled. Some people with fibromyalgia may not tolerate steroids, but this is not a universal problem. Make sure to discuss treatment options, and any side effects you experience, with your doctor to determine the best treatments for you.

Here's an article with lots of great information on PMR, from Verywell.com Arthritis Expert Carol Eustice:

Sources:

Caro XJ, Winter EF. Arthritis & rheumatology. 2014 Jul;66(7):1945-54. Evidence of abnormal epidermal nerve fiber density in fibromyalgia: clinical and immunologic implications.

Caro XJ, Winter EF, Dumas AJ. Rheumatology. 2008 Feb;47(2):208-11. A subset of fibromyalgia patients have findings suggestive of chronic inflammatory demyelinating polyneuropathy and appear to respond to IVIg.

Docken, William P, MD. American College of Rheumatology. Polymyalgia Rheumatica. All rights reserved. Accessed: May 2016.

Haliloglu S, et al. Rheumatology international. 2014 Sep;34(9):1275-80. Fibromyalgia in patients with other rheumatic diseases: prevalence and relationship with disease activity.

Liptan, GL. Journal of bodywork and movement therapies. 2010 Jan;14(1):3-12. Fascia: A missing link in our understanding of the pathology of fibromyalgia.

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