The Differences Between Fibromyalgia and Polymyalgia Rheumatica

An elderly woman clutches her painful shoulder

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Fibromyalgia and polymyalgia rheumatica (PMR) involve chronic pain and can seem similar. However, they're different conditions, with fibromyalgia characterized by the central nervous system's abnormal processing of pain and other sensory signals, and PMR involving inflammation in the muscles that's likely autoimmune in nature.

Because of their surface similarities, it's possible for PMR to be misdiagnosed as fibromyalgia or vice versa, or for either condition to be overlooked in someone who's already diagnosed with the other.

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 Fibromyalgia?

In fibromyalgia, the central nervous system takes pain signals and "turns up the volume" through a complex mechanism that's believed to involve extra nerve structures, abnormal nerve function, and neurotransmitter imbalances in the brain.

While fibromyalgia does involve some amount of immune-system dysfunction and some cases may have an inflammatory component, this condition is not classified as autoimmune or inflammatory. (Some subgroups may involve autoimmunity but research is still inconclusive on that.) Fibromyalgia is a neurological condition that many experts consider to be on the spectrum of central sensitivity syndromes. It's sometimes referred to as a neuroimmune or a neuro-endocrine-immune condition because of its complexity.

The most common fibromyalgia symptoms include:

Fibromyalgia pain can be all over the body, not only confined to particular places. By definition, pain must be present in the spine and in all four quadrants of the body. Each individual can have places where their pain is typically worst, but most people with this illness have some degree of pain all over their bodies.

This condition can cause any of a few dozen other potential symptoms, as well. They may come on suddenly, especially after an illness or physical trauma (surgery, car accident, childbirth) or develop slowly over several months or even years.

What is Polymyalgia Rheumatica?

PMR is an inflammatory disease that's believed to be autoimmune, meaning that the body is attacking its own healthy tissues because it mistakes them for infectious agents such as viruses or bacteria. This condition is seen almost exclusively in people over 65. Doctors may not even consider it in someone who's not a senior citizen.

Among people older than 50, about 0.5% have PMR, making it a rare disease. (To give you a comparison, fibromyalgia impacts between 2% and 4% of the U.S. population.)

A 2014 study in Rheumatology International suggested that PMR may be present in about 3% of people with fibromyalgia. If that's true, it'd make it considerably more common in people with fibromyalgia 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.

Fibromyalgia vs. Polymyalgia Rheumatica
Features Polymyalgia Fibromyalgia
Inflammation High levels, joints and muscles Absent or at low levels, possibly in the fascia
Autoimmunity Has features of autoimmunity Some subgroups may involve autoimmunity
Age Most common over 65 Most common in women of childbearing age
Pain Locations Specific areas Widespread
Time of Day Pain often worst in morning Pain often worse at night
Differentiating Symptoms Low-grade fever, loss of appetite, malaise Abnormal pain types, cognitive dysfunction, sensitivities
Onset Usually rapid May be rapid or develop over time

Diagnosis and Treatment

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 elevated sed rate is an indicator of inflammation.

In people with fibromyalgia, the sed rate is typically normal or just slightly elevated. Along with symptoms, fibromyalgia can be diagnosed by a tender-point exam, in which the doctor checks for a heightened pain response but putting pressure on specific points throughout the body; or by a set of two questionnaires that evaluate the full range of symptoms and their severities.

PMR is generally treated with steroids and can often be well controlled. Steroids are not considered effective in fibromyalgia and achieving control is difficult. Fibromyalgia treatment regimens generally include multiple approaches, including:

  • Medications, such as anticonvulsants and/or antidepressants
  • Supplements
  • Acupuncture
  • Physical therapy, gentle massage therapy, or chiropractic treatments
  • Low-impact, specifically tailored exercise, such as warm-water exercise, yoga, Tai Chi, and qi gong

Make sure to discuss treatment options and any side effects you experience with your doctor to determine the best ones for you.

A Word From Verywell

If you suspect you have one or both of these conditions, bring it up with your doctor. You're the expert on your pain, which is invisible to the doctor, so be prepared to describe its nature and behavior and make a case for why you believe it's one of these conditions or the other (or both.) The diagnostic process may not be easy, but it's important for you to keep pushing until you have answers, and ideally treatments, that you're happy with.

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