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Clin Ther. 2019 Feb 20. pii: S0149-2918(19)30003-7. doi: 10.1016/j.clinthera.2018.12.016. [Epub ahead of print]

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Fibromyalgia: Definitions, Similarities, and Differences.

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Department of Neurology, Pain & Fatigue Study Center, Icahn School of Medicine at Mount Sinai, New York, NY, USA. Electronic address:


This commentary presents a simplified way of making the diagnosis of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) using the 1994 Centers for Disease Control and Prevention case definition. The format used can easily be modified for other case definitions. The commentary then discusses whether ME/CFS is the same or a different illness from fibromyalgia. Because overlap exists between the 2 syndromes, some investigators have posited that they are variants of the same illness. I have viewed this as an empirically testable hypothesis and have summoned considerable amounts of data that suggest that the 2 illnesses differ. Were differences to exist, that would suggest different pathophysiologic processes for each, leading to different treatments.


fatigue; overlap; pain; unexplained illness

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