FM and ME/CFS – The Same, Related, or Different?

The question as to whether fibromyalgia and ME/CFS ('chronic fatigue syndrome') are the same illness, closely related illnesses, or completely different illnesses has been debated by physicians and scientists for many years.

Some feel FM and ME/CFS are different facets of the same illness, while others believe they are distinct disorders that share several common symptoms. To further complicate the situation, 70 percent of people who have been diagnosed with one are also diagnosed with the other.

A new paradigm put forth several years ago by Muhammad B. Yunus, MD, suggests that FM and ME/CFS, along with a number of other conditions like irritable bowel syndrome, migraines, and multiple chemical sensitivities, are part of a larger group he terms “Central Sensitivity Syndromes.” The uniting factor that all of these illnesses have in common is central sensitization – an exaggerated response of the central nervous system to stimuli.

Overview of FM and ME/CFS

Before enumerating their similarities and differences, let’s look at a brief overview of FM and ME/CFS.

FM (Fibromyalgia) is a malfunction of the central nervous system that causes disordered pain processing, and results in pain amplification. The primary symptoms of FM are:

• Widespread chronic pain

• Extreme fatigue

• Sleep problems.

Other symptoms that may occur include: allergies, irritable bowel, irritable bladder, headaches, migraines, dizziness, numbness and tingling, sensitivity to cold or heat, depression, restless legs syndrome, chemical or environmental sensitivities, impaired balance or coordination, dry eyes and mouth, vision problems, or problems with memory, concentration and cognitive functioning.

ME/CFS – (Myalgic Encephalopathy or Myalgic Encephalomyelitis / Chronic Fatigue Syndrome) is an illness characterized by prolonged and debilitating fatigue accompanied by a number of other symptoms, including: memory and concentration problems, recurrent sore throats, unrefreshing sleep, muscle and joint pain, and headaches.

Generally speaking, ME/CFS includes at least four of the following:

• Post-exertional malaise lasting more than 24 hours

• Non-refreshing sleep

• Short-term memory or concentration problems

• Muscle pain

• Multi-joint pain without joint swelling or redness

• Headaches of a new type, pattern or severity

• Tender cervical or axillary lymph nodes

• Sore throat.

Over the years, there have been a number of definitions of ME/CFS. The best thus far seems to be the new Canadian Definition. You can download a full copy of the Canadian Definition here (

Comparing and Contrasting

While the two illnesses have a number of similarities, they also have some distinct differences.

Similarities – In addition to some symptom similarities, FM and ME/CFS have several things in common:

• Reduced cerebral blood flow to the cortex and midbrain

• HPA (hypothalamic pituitary axis) suppression

• Reduced levels of serotonin

• Non-restorative sleep

• Reduced levels of growth hormone

• Evidence of a genetic component.

Differences – Although there are many similarities, there are also significant differences.

• FM is identified by 18 distinct tender points (designated points on the body that are painful when four kilograms of pressure are applied), while ME/CFS is distinguished by post-exertional malaise (deep fatigue and exhaustion following physical exertion, which lasts more than 24 hours).

• Substance P (a neurotransmitter that sends pain signals) is elevated in FM but not in ME/CFS.

• RNaseL (a cellular antiviral enzyme) is frequently elevated in ME/CFS but not in FM.

• ME/CFS is often triggered by an infectious or flu-like illness, while FM is usually triggered by a severe physical or emotional trauma (for example, injury, illness, surgery, prolonged stress).


• Getting an accurate diagnosis of either disorder can be difficult – to say the least.

• People are rarely diagnosed with both at the same time or by the same doctor.

• Even though each illness has its own set of diagnostic criteria, sometimes the diagnosis you receive may depend more on which one your doctor is most familiar with.

• The fact that such a large percentage of patients have both FM and ME/CFS makes it especially difficult to distinguish between them.


• Treatment of both FM and ME/CFS is primarily aimed at relieving symptoms.

• To date three medications have received FDA approval for the treatment of FM. No medication has yet been approved for treating ME/CFS, but clinical trials are being conducted and an FDA decision on the antiviral/immune modulating drug Ampligen® is expected soon.

• It is becoming apparent that there are a number of subtypes of ME/CFS, which further complicates the search for effective treatments.

• It’s usually a matter of trial and error for patients with either illness to find an effective treatment plan.

• Most who have had some success in improving symptoms report using a combination of medication, alternative/complementary therapies and lifestyle changes.

* Karen Lee Richards is the Expert Patient, specializing in Fibromyalgia and Chronic Fatigue Syndrome, for HealthCentral's ChronicPainConnection ( For more information about Karen, who co-founded the National Fibromyalgia Association (NFA) with Lynne Matallana in 1997, see “Karen Lee Richards – Making a difference in the lives of those living with Fibromyalgia and Chronic Fatigue Syndrome."

Note: This information has not been evaluated by the FDA. It is generic and is not meant to prevent, diagnose, treat or cure any illness, condition, or disease. It is very important that you make no change in your healthcare plan or health support regimen without researching and discussing it in collaboration with your professional healthcare team.

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