Chronic Fatigue Syndrome Has a New Name – Systemic Exertion Intolerance Disease

Many healthcare providers struggle with the diagnosis of chronic fatigue syndrome (CFS).

  • Is it real or psychosomatic?
  • Does it follow an infection such as Lyme disease?
  • How does it differ from fibromyalgia or irritable bowel syndrome?

Because of these complexities, the Institute of Medicine (IOM) was asked by several federal agencies to review the evidence base for CFS.

In 2015 they recommended a new name systemic exertion intolerance disease or SEID.

Why Systemic Exertion Intolerance Disease


Chronic Fatigue Syndrome

Why the Name Change?

It is thought that the term “chronic fatigue syndrome” perpetuates a misunderstanding of the illness and contributes to the dismissive attitudes of healthcare providers and the public.  Also, the other term used to describe the disorder, “myalgic encephalomyelitis” is inappropriate because there is a lack of evidence for encephalomyelitis, and myalgia is not a core symptom of the disease.

The name proposed systemic exertion intolerance disease or SEID captures a central characteristic of the disease: the fact that exertion of any sort—physical, cognitive, or emotional—can adversely affect patients in many organ systems and in many aspects of their lives.


For patients and physicians alike, conditions presenting complex symptoms have been challenging over the years. In the late 1800s, the term “Americanitis” was coined by William James, a famous psychologist. He thought the symptoms, sometimes referred to as neurasthenia, were a result of the fast-paced, American, capitalistic lifestyle that caused a great deal of stress. This idea lost favor in the 1920s.

During the 30s and 40s, it was thought that pathogens could be the cause of the symptoms and later Lyme disease was considered as a probable cause.

Chronic fatigue syndrome was first used in medical literature to describe an illness that seemed like a chronic active Epstein-Barr virus (EBV) infection. In 1988, the term was defined in a publication: “Chronic fatigue syndrome: a working case definition.”

Take Away

Our understanding of a disease is formed by the language used to identify it. Although the IOM proposed systemic exertion intolerance disease, or SEID as the new name to better describe CFS in 2015, I think we can still consider it an emerging term. Up to Date, Mayo Clinic, and many other reputable institutions are now using it in their publications. Strangely enough, although its own ICD-10 was recommended by the IOM committee, it appears to still fall under CFS (chronic fatigue syndrome). Granted systemic exertion syndrome or SEID does not easily roll off one’s tongue, but I recommend you add to your vocabulary, and if you are an instructor, add it to your medical terminology course content.


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