Chronic Fatigue Syndrome (CFS)/ ME
Chronic fatigue syndrome (CFS) is a serious disorder characterised by persistent post-exertional fatigue and substantial symptoms related to cognitive, immune and autonomous dysfunction. Disease mechanisms are complex with no single causal factor identified. Yet there are indications that infections and immunological dysfunction contribute to development and maintenance of symptoms, probably interacting with genetic and psychosocial factors.
Holmes et al coined the term ‘chronic fatigue syndrome’ in 1988, as an alternative to ‘The chronic Epstein-Barr virus syndrome’. Since this case definition—the CDC-1988/Holmes Criteria—was presented in 1988, numerous revisions have been developed, aiming for distinctive and reliable identification of individuals who represent a homogenous and consistent phenotype of the hypothesised disease entity, consistent with pathophysiological and psychosocial findings. Currently, the term ‘myalgic encephalomyelitis’ (ME) is commonly used to conceptualise a specific neuroimmunological condition, assumed to be more severe and less psychologically attributed than CFS. In 2003, Carruthers et al presented the Canadian-2003 Criteria for diagnosis of ME/CFS. A revised version was presented as International Consensus Criteria (the ICC-2011 Criteria) for ME, claiming to be a selective case definition for identification of patients with neuroimmune exhaustion with a pathologically low threshold of fatigability and symptom flare after exertion. The assertion that CFS and ME are different clinical entities is disputed.
Myalgic Encephalomyelitis (ME) and chronic fatigue syndrome (CFS) were names given to two well-documented cluster outbreaks of a clinically similar illness in London, UK in 1955 and in NV, USA in 1984. Several different but overlapping case definitions have been published for ME and for CFS to aid in diagnosing sporadic cases. Research studies tend to use the term CFS because a case definition was written for this purpose. The name CFS has been criticized for trivializing the illness and it can be confused with the non-specific term chronic fatigue, which is a common symptom in other illnesses. The World Health Organization classifies ME as a disease of the central nervous system.
Less common names for the illness include chronic fatigue immune dysfunction syndrome, myalgic encephalopathy, and neuro-endocrine-immune dysfunction syndrome. In 2015 a new name, systemic exertion intolerance disease (SEID) and a new case definition were suggested. Currently, the new name is under discussion and the new case definition has not yet been clinically validated. This publication will use the acronym ME/CFS.
Symptoms of ME/CFS sometimes follow an acute illness, such as influenza or infectious mononucleosis. If symptoms resolve within 6 months, the term post-infectious fatigue syndrome is used to describe the illness.