myalgic encephalomyelitis/chronic fatigue syndrome

myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), complex condition characterized by persistent debilitating fatigue that has no identifiable cause. Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a remarkably complex illness and remains incompletely understood. These factors complicate its accurate diagnosis and have raised questions regarding its naming and description.

Epidemiology and characteristics

Worldwide, an estimated 0.2 to 2.8 percent of people are affected by ME/CFS. However, prevalence rates likely are much higher because an estimated 90 percent of persons living with ME/CFS may be undiagnosed. There are various reasons for such drastic underdiagnosis; some examples include limited access to health care, a lack of knowledge about ME/CFS among health care providers, a lack of acceptance by some members of the medical community, the absence of tests to detect ME/CFS, and fatigue being a ubiquitous symptom of illness. Indeed, while fatigue can undermine a person’s ability to work and carry out day-to-day tasks, physicians generally consider fatigue to be a nonspecific symptom, causing it to be readily overlooked. Moreover, although anyone can be affected by ME/CFS, it is most common in adults between ages 40 and 60 and tends to affect women more often than men; this age range and gender difference presents significant challenges, particularly in differentiating ME/CFS from symptoms of early menopause.

Historical developments

Some of the first reports of “outbreaks” of fatigue syndrome were made in the 1930s and often involved polio patients. Such clusters of fatigue onset among hospitalized patients instilled the idea that the condition was potentially infectious. In 1970 a review of reported outbreaks led to the conclusion that fatigue syndrome, then known as benign myalgic encephalomyelitis, was a psychosocial phenomenon, rather than a specific physical disorder. In the mid-1980s the term benign was discarded, and diagnosis of myalgic encephalomyelitis (ME) was based on prolonged muscle fatigue following mild physical effort. Shortly thereafter health officials in the United States renamed the condition chronic fatigue syndrome (CFS), leaving ME as a synonym.

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Through much of the 1990s and into the early 2000s, the validity of CFS as a distinct disorder was questioned, especially because of the considerable overlap with other functional somatic syndromes, such as fibromyalgia and Gulf War syndrome. In addition, some patients felt stigmatized by use of the term fatigue, and, because symptoms arise in multiple body systems and involve more than fatigue, there was considerable pressure to rename the condition. Additionally, some experts considered ME and CFS to be two distinct conditions. The name systemic exertion intolerance disease (SEID) was proposed in 2015 in a report by the U.S. Institute of Medicine (IOM; later the National Academy of Medicine). Today, because of the condition’s complexity, it is generally referred to by using the umbrella term ME/CFS, though, in the view of some, this remains inadequate.

Suspected causes, diagnosis, and treatment

Multiple theories about the cause of ME/CFS have been advanced, but none have been proved. Suggested causes include bacterial or viral infections, genetic factors (the condition appears to run in families), physical injury or emotional trauma, metabolic disorders, and altered immune function.

Diagnosis of ME/CFS is based on the presence of the following criteria, wherein symptoms have been present for more than six months and are moderate to severe in intensity at least half of the time.

In addition, one of the following—cognitive impairment or orthostatic intolerance (symptoms are worse when standing and are relieved by lying down)—must also be present in order for the condition to be diagnosed as ME/CFS.

Individuals may experience a host of other symptoms as well, including sore throat, tender lymph nodes, muscle pain and weakness, joint pain, digestive issues, allergies or sensitivity to specific stimuli (e.g., light), headache, sleep disorders, confusion, and memory loss. Symptoms are often similar in appearance to those of other conditions and tend to come and go or may fluctuate in severity over time. Thus, diagnosis of ME/CFS further requires all other illnesses or medical conditions associated with the same symptoms to be ruled out clinically.

There is no cure for ME/CFS. Patients can be treated with drugs to control their most severe symptoms; for example, some patients are treated with antihistamines to control allergy-like symptoms or with sedatives to treat sleep disorders. Many patients respond positively to a range of nondrug therapeutic approaches, including exercise therapy, counseling, and stress reduction. In addition, studies have shown promising responses to cognitive behavioral therapy, in which patients learn to develop strategies that help them cope with their condition and that improve the quality of their lives. While some persons with ME/CFS become progressively worse, most improve gradually, and some eventually achieve full recovery.