Sir, Although many doctors equate chronic fatigue syndrome (Oxford definition) with what we call myalgic encephalomyelitis (ME), there are some noteworthy differences.
Firstly, in Britain, chronic fatigue syndrome is an umbrella term covering a number of different conditions including neurasthenia, effort syndrome and fibromyalgia. ME is a more specific entity (see the ‘ 10, 1992) and unlike the above, has been closely linked to a persistent infection and immune system activation.
Secondly, while profound fatigue is undeniably the most common symptom of ME, it is rather different from the type of tiredness which people normally experience after exertion. For example, it is often accompanied by feelings of illness which are so unlike anything which people have had before that patients frequently say they cannot describe it. Some have referred to the latter as a severe ‘flu-like’ malaise, others have likened it to being poisoned. Regrettably, having subsumed ME under a general heading of chronic fatigue syndrome, this important and disabling aspect of ME will almost certainly be overlooked.
You can read the rest of this letter here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2399627/pdf/postmedj00050-0083a.pdf
Source: Macintyre A, Hume MC. The chronic fatigue syndrome. Postgrad Med J. 1993 Feb;69(808):164. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2399627/