Chronic fatigue syndrome is characterised by debilitating severe fatigue persisting for more than six months. Furthermore, it is associated with physical symptoms, such as mild fever, sore throat, arthralgia, and myalgia, as well as psychological symptoms such as headache, insomnia, depressive state, and neuropsychiatric symptoms. It has often been claimed that the onset of chronic fatigue syndrome follows an infection or infection-like illness; hence a certain microorganism(s) or virus may cause it. Another possible candidate for inducing chronic fatigue syndrome is cellular or humoral immune dysfunction, which has been found in patients with the disease. There is controversy also as to whether or not chronic fatigue syndrome and major depression (mood disorder) represent different entities.
Mild fever, pharyngitis, and lymphadenopathy, which are suggestive of the existence of inflammation, are often associated with chronic fatigue syndrome, but the peripheral leucocyte count, erythrocyte sedimentation rate, and C-reactive protein concentration are usually normal in patients with chronic fatigue syndrome. Hence, it is possible that certain cytokines may produce the symptoms in patients with chronic fatigue syndrome and, possibly, those with major depression. For example, interferon is known to cause fever, fatigue, and psychoneurological abnormalities. We conducted this study to clarify whether or not 2′,5′-oligoadenylate synthetase (2,5-AS), neopterin, adenosine deaminase, endotoxin, or B-glucan participate in the pathogenesis of chronic fatigue syndrome.
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Source: Matsuda J, Gohchi K, Gotoh N. Serum concentrations of 2′,5′-oligoadenylate synthetase, neopterin, and beta-glucan in patients with chronic fatigue syndrome and in patients with major depression. J Neurol Neurosurg Psychiatry. 1994 Aug;57(8):1015-6. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1073106/