The Difference Between Fibromyalgia and Polymyalgia Rheumatica

Both fibromyalgia and polymyalgia rheumatica (PMR) involve chronic pain and can seem similar. However, they're very different conditions. Fibromyalgia is a condition in which pain and other sensory signals are not processed normally by the central nervous system. PMR, though, while characterized by musculoskeletal pain and stiffness, is related to inflammation that's likely autoimmune in nature.

Because of their apparent similarities, it's possible for PMR to be misdiagnosed as fibromyalgia or vice versa. It's also possible 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:

• Hyperalgesia (amplified pain)
• Abnormal pain types such as allodynia (pain from stimuli that shouldn't be painful) and paresthesia (abnormal nerve sensations, such as "zings" or tingling)
• Cognitive dysfunction, often called "fibro fog," which can involve language impairment, poor short-term memory, and inability to multitask
• Fatigue
• Sensitivities to heat, cold, light, noise, chemical fragrances, and food

Fibromyalgia pain is not confined to certain areas and it can be all over the body. 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. The effects 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 organisms such as viruses or bacteria. This condition is seen almost exclusively in people over the age of 50.

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.)

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 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.

Is Polymyalgia Rheumatica Worse Than Fibromyalgia?

Every person’s experience is different, so it’s impossible to say definitively whether one disorder is worse than another. However, there are aspects of fibromyalgia that may make it harder to manage than PMR. For instance:

• Fibromyalgia can occur at any age, making it harder to work and parent. 
• It is a chronic disorder that can be difficult to control while polymyalgia can usually be managed with steroids.
• Eventually, PMR goes away while fibromyalgia is a lifelong condition.
• Fibromyalgia has been associated with higher than average levels of PTSD.

The pain associated with fibromyalgia, while real, is not dangerous or life-threatening. However, untreated inflammation, such as that which can occur in PMR, can lead to joint damage, as well as increased risk of cardiovascular morbidity and mortality.

Diagnosis

No single blood test can diagnose PMR. Healthcare providers consider the full range of symptoms along with blood tests that measure C-reactive protein and blood sedimentation (or "sed") rate. Elevated results for either test indicate 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 healthcare provider checks for a heightened pain response but putting pressure on specific points throughout the body. Sometimes a set of two questionnaires that evaluate the full range of symptoms and their severities is used in the diagnosis of this condition.

Why Is Polymyalgia Mistaken for Fibromyalgia?

The difficulty in diagnosing PMR can lead to confusion and a possible misdiagnosis at first. Cases in which the circumstances match common fibromyalgia situations, such as women who feel pain in the shoulders and arms, are more likely to be initially classified as fibromyalgia until further tests can show it to be PMR.

Treatment

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 healthcare provider to determine the best ones for you.

A Word From Verywell

If you suspect you have one or both of these conditions—polymyalgia rheumatica and fibromyalgia—bring it up with your healthcare provider. You're the expert on your pain, which is invisible to the healthcare provider, so be prepared to describe its nature, triggers, and timing in detail. The diagnostic process may not be easy, but it's important to be patient and persistent so you can ultimately get the right management plan to relieve your symptoms.