Differences Between Fibromyalgia and Myalgic Encephalitis/Chronic Fatigue Syndrome


Fibromyalgia (FM) is a chronic pain syndrome that involves widespread muscle pain (myalgias) and joint pain (arthralgias). Fibromyalgia is thought to be due to a dysfunction in the way the brain and spinal cord process painful and non-painful signals, causing pain amplification.

Myalgic encephalitis (ME), also known as chronic fatigue syndrome (CFS), is a condition involving profound fatigue that can’t be explained by another underlying medical condition. ME/CFS worsens with physical exertion and does not improve with rest. Several features of FM and ME/CFS overlap, however; they are distinct conditions with different symptoms and causes.


Both myalgic encephalitis/chronic fatigue syndrome and fibromyalgia are diagnoses of exclusion, meaning there are no definitive medical tests that can diagnose either condition. The two conditions share several symptoms:


Characteristics that are more definitive of ME/CFS include the following:

  • Fatigue more prominent symptom than pain
  • Flu-like symptoms, such as sore throat, night sweats, and chills
  • Swollen lymph nodes
  • Often triggered by a virus, such as mononucleosis

Characteristics of FM that are not as common with ME/CFS include the following:

  • Pain is more debilitating than fatigue. This may include symptoms of allodynia (pain associated with non-painful stimuli) and hyperalgesia (unusually amplified pain).
  • Symptoms of fibromyalgia often begin after a trauma, such as a car accident.