Chronic Fatigue Syndrome vs. Fibromyalgia: What's the Difference?

Apples to Apples, or Apples to Oranges?

Nine OK/Getty Images

What's the difference? The issue of chronic fatigue syndrome vs. fibromyalgia concerns many people, including doctors, the people who have these disorders, and the family and friends who care about them.

Some doctors treat fibromyalgia (also called fibromyalgia syndrome, or FMS) and chronic fatigue syndrome (CFS, also called myalgic encephalomyelitis, or ME/CFS) separately, while others believe they are actually the same disorder—or, at least, variations of it.

According to the Arthritis Foundation, research shows that between 50 and 70 percent of people with one diagnosis also fit the criteria for the other. That could be due to a couple of factors:

  1. their similarities
  2. a substantial overlap between them (meaning people who have both conditions)
  3. the lack of definitive blood tests or scans for diagnosing them

Here's a look at the similarities and differences of these two illnesses.

Similarities: Symptoms

FMS and ME/CFS are known to have a number of symptoms in common. They include:

Many symptom triggers are the same, as well, such as:

  • stress (physical or psychological)
  • injury
  • acute illness
  • worse-than-usual sleep
  • exertion

They're also linked to many of the same commonly overlapping conditions, including:

Why the similarities? The prevailing theory is common underlying features. Chief among those is dysregulation of multiple brain chemicals called neurotransmitters.

Over the years, researchers have come up with a variety of classifications for FMS, ME/CFS, and similar conditions, such as functional somatic syndromes, multi-system illnesses, neuroimmune disorders, and neuroendocrineimmune disorders.

More recently, yet another term has come into play and appears to be more readily accepted by the medical community it is "central sensitivity syndrome," or CSS.

The CSS's have a key feature in common—they all involve central nervous systems that have become highly sensitive to certain things. Depending on the condition, they could be sensitive to touch, temperature, certain foods, chemicals/fragrance, noise, light, and an array of other environmental factors. All of the overlapping conditions listed above fall under this umbrella term, as do several others.

Differences: Symptoms

The differences in symptoms are often more of a case of degree than complete separation. For instance, the primary symptom in ME/CFS is fatigue, while the primary symptom of FMS is pain. However, both conditions may involve both fatigue and pain.

ME/CFS is more likely to be tied to flu-like symptoms, including:

  • sore throat
  • swollen glands
  • frequent low-grade fever

FMS always includes pain, including hyperalgesia (amplified pain) and sometimes tactile allodynia (pain from light touch).

Many cases of ME/CFS include one or both of these pain types, as well. However, FMS involves other pain types not common in ME/CFS.

Both conditions involve an extreme reaction to exertion, but this is typically far more profound in ME/CFS and is called post-exertional malaise.

While these two conditions share many overlapping conditions, FMS is linked to several pain conditions and sleep disorders that do not appear to be linked to ME/CFS.

Similarities: Treatment

With such similar symptoms and a major feature in common, it should come as no surprise that FMS and ME/CFS are often treated the same way.

For example, doctors frequently prescribe the same drugs for them, including:

Other kinds of treatments that may be recommended for both of these conditions include:

Differences: Treatment

Again, differences aren't extreme when it comes to treatment.

In FMS, treatment tends to be more focused on pain relief. In ME/CFS, it skews more toward fatigue management. However, it's often the same drugs and other treatments that help with both of these symptoms.

One major difference is that some doctors believe ME/CFS is tied to certain viruses, and they may prescribe antiviral drugs. This is an exception to the rule, though, as most doctors aren't convinced of a viral component.

Similarities: Diagnosis

The way these conditions are diagnosed is another similarity. Both of them are diagnoses of exclusion, which means they don't have the kind of diagnostic tests people have come to expect.

No blood test or scan can tell you whether you do (or don't) have FMS or ME/CFS. Instead, doctors rely heavily on things like what symptoms you have and tests to rule out conditions that cause similar symptoms.

Differences: Diagnosis

With ME/CFS, the diagnosis of exclusion is all we have that's widely accepted. Some practitioners have developed their own diagnostic methods that they say are effective, but none has yet been proven effective or accepted by the medical community.

FMS does have a couple of tests, but they're not your standard type of medical tests.

The first is called a tender-point exam. Basically, a doctor looks for certain symptoms accompanied by pain at specific sites around the body.

Another diagnostic method involves a set of symptoms along with answers to a questionnaire. Research suggests that both methods are quite effective at diagnosing FMS and differentiating it from similar conditions.

Similarities: Perceptions

Perceptions are important issues for these conditions. Both have faced widespread skepticism in the medical community, the legal community, and society at large.

Even after decades of medical research, you can still find some doctors and other health-care workers who don't "believe" in one or both of them. That can lead to inadequate treatment and, in extreme cases, even hostility and ridicule toward the sick person.

Judges who don't believe in them may deny claims for Social Security Disability Insurance. In divorce and custody matters, these diagnoses have been used to support the spouse's claims that the sick person is "crazy" or "malingering."

Countless marriages, other romantic relationships, friendships, and family bonds have been destroyed by misunderstandings of or disbelief in FMS or ME/CFS.

Differences: Perceptions

The difference in perceptions has grown over time. They used to be about on the same footing. Then came FDA approval of the first FMS drug, Lyrica (pregabalin) in 2007. That's had a legitimizing effect on the condition.

Since then, FMS has become far more accepted medically, legally, and socially than it used to be. That's  begun to make things easier on those who have it.

Sadly, ME/CFS still has no medications that are FDA approved for it, so while it's less stigmatized than it once was, the gains have been much slower and smaller.

The name "chronic fatigue syndrome" is believed to be a major cause of this problem because it sounds like someone is just tired and needs a good nap. That's why some researchers, patients, and advocacy groups have pushed to have "ME" added to the name and hope that it'll someday replace "CFS" altogether.

A major medical report published in 2015 could help legitimize ME/CFS for the remaining skeptics. The most significant part is that it formally recognized ME/CFS as a disease instead of syndrome. It remains to be seen what the long-term impact of that will be.

Do the Differences Matter?

Actually, some experts say the differences between these two conditions probably don't matter all that much.

Why? Mainly because the treatments are so similar. If diagnosis A and diagnosis B lead to the same treatment, does it matter which one you have?

As we learn more about them, though, the differences may grow more distinct. If treatments diverge over time, based on what's gone wrong in the body rather than on symptoms, we could end up with medications that work much better for one or the other.

Until then, we'll be counted as more alike than different and will face the same situation: living with a potentially debilitating chronic illness, and searching for treatments that help alleviate our many (very similar) symptoms.