This has been posted before but I thought I'd repost as many have brought up symptoms of temperature dysregulation, weight changes.....which can be part of CFS. Note that the U.S. CDC criteria are much narrower (was orginally conceived for research purposes. The Canadian are more inclusive of the multiple symptoms people with CFS have. ************************************************************ The Canadian Clinical Case Definition is summarized as follows: 1. POST-EXERTIONAL MALAISE AND FATIGUE: There is a loss of physical and mental stamina, rapid muscular and cognitive fatigability, post-exertional fatigue, malaise and/or pain, and a tendency for other symptoms to worsen. A pathologically slow recovery period (it takes more than 24 hours to recover). Symptoms exacerbated by stress of any kind. Patient must have a marked degree of new onset, unexplained, persistent, or recurrent physical and mental fatigue that substantially reduces activity level. [Editor’s note: The M.E. Society prefers to use “delayed recovery of muscle function,” weakness, and faintness rather than “fatigue.” Further, we disagree that the muscle dysfunction and post-exertional sickness is “unexplained.” See our Cardiac Insufficiency Hypothesis page and our Research-Based Subsets page for researchers’ medical explanations on this website.] 2. SLEEP DISORDER: Unrefreshing sleep or poor sleep quality; rhythm disturbance. 3. PAIN: Arthralgia and/or myalgia without clinical evidence of inflammatory responses of joint swelling or redness. Pain can be experienced in the muscles, joints, or neck and is sometimes migratory in nature. Often, there are significant headaches of new type, pattern, or severity. [Editor’s note: neuropathic pain is a common symptom and should be added here as well.] 4.NEUROLOGICAL/COGNITIVE MANIFESTATIONS: Two or more of the following difficulties should be present: confusion, impairment of concentration and short-term memory consolidation, difficulty with information processing, categorizing, and word retrieval, intermittent dyslexia, perceptual/sensory disturbances, disorientation, and ataxia. There may be overload phenomena: informational, cognitive, and sensory overload -- e.g., photophobia and hypersensitivity to noise -- and/or emotional overload which may lead to relapses and/or anxiety. 5. AT LEAST ONE SYMPTOM OUT OF TWO OF THE FOLLOWING CATEGORIES: AUTONOMIC MANIFESTATIONS: Orthostatic Intolerance: e.g., neurally mediated hypotension (NMH), postural orthostatic tachycardia syndrome (POTS), delayed postural hypotension, vertigo, light-headedness, extreme pallor, intestinal or bladder disturbances with or without irritable bowel syndrome (IBS) or bladder dysfunction, palpitations with or without cardiac arrhythmia, vasomotor instability, and respiratory irregularities. [Editor’s note: low plasma and/or erythrocyte volume should be added as another explanation for orthostatic intolerance in this disease. More cardiac symptoms should be listed such as left-side chest aches and resting tachycardias, which, in addition to low blood volume, have also been documented in the research. The full text of the case definition does suggest 24-hour Holter monitoring, and when tachycardias with T-wave inversions or flattenings are present that they not be labeled as nonspecific since they aid in the diagnosis of ME/CFS. The frequent tachycardias seen in ME/CFS have been shown by Dr. Paul Cheney to be a compensatory mechanism that serves to increase cardiac output in the presence of low stroke volume due to diastolic dysfunction in the heart. Orthostatic problems may also be related to diastolic dysfunction as recently shown by Dr. Paul Cheney. See our Cardiac Insufficiency Hypothesis page.] NEUROENDOCRINE MANIFESTATIONS: loss of thermostatic stability, heat/cold intolerance, anorexia or abnormal appetite, marked weight change, hypoglycemia, loss of adaptability and tolerance for stress, worsening of symptoms with stress and slow recovery, and emotional lability. IMMUNE MANIFESTATIONS: tender lymph nodes, sore throat, flu-like symptoms, general malaise, development of new allergies or changes in status of old ones, and hypersensitivity to medications and/or chemicals. 6. The illness persists for at least 6 months. It usually has an acute onset, but onset also may be gradual. Preliminary diagnosis may be possible earlier. The disturbances generally form symptom clusters that are often unique to a particular patient. The manifestations may fluctuate and change over time. Symptoms exacerbate with exertion or stress.