Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines. You may find the Chronic Fatigue Syndrome (Myalgic Encephalomyelitis) article more useful, or one of our other health articles.
Synonym: myalgic encephalopathy
Myalgic encephalomyelitis or chronic fatigue syndrome (ME/CFS) is a complex, chronic medical condition of unknown aetiology characterised by symptom clusters that include:
- Fatigue and malaise that is worse after exertion.
- Cognitive dysfunction.
- Immune dysfunction.
- Unrefreshing sleep.
- Autonomic dysfunction, and also
- Neuroendocrine symptoms.
The condition is common and is often severely disabling.
ME can cause severe functional impairment and very poor quality of life. Research has indicated that significant abnormalities in the central nervous system, immune system, endocrine system and muscles contribute to the disease process.
ME is classified by the World Health Organization (WHO) as a neurological disease, and this classification is recognised by the Department of Health, Medical Research Council and the National Institute for Health and Care Excellence (NICE).
Diagnosing the disease remains a challenge. Patients often struggle with their illness for years before an identification is made. Once diagnosed, patients often complain of receiving hostility from their healthcare provider as well as being subjected to treatment strategies that exacerbate their symptoms.
- ME is not uncommon but the true prevalence is unknown and depends on the criteria used for diagnosis.
- However, it is estimated that ME affects about 0.2-0.4% of the population (about 250,000 people in the UK), including children and adolescents.
- ME affects all social classes and ethnic groups.
- Women appear to be affected more than men, with the ratio reported as being female:male 2:1.
- ME can affect children and research has shown a higher incidence in socially deprived families.
- ME is a relatively common cause of long-term sickness absence from school.
- ME can often be linked to a previous viral infection. In other cases, ME appears to follow a vaccination, or other known triggering event.
- Epidemics of ME have been reported in several areas but no causative organism has been found. There is some debate as to whether the chronic fatigue associated with these outbreaks may be a different form of the disorder.
- ME can affect more than one family member – suggesting that genetic factors are involved.
Sometimes reaching a diagnosis can be problematic for a number of reasons:
- The onset may be relatively sudden or gradual, following a physical illness or stressful event, or apparently out of the blue.
- The range of presenting symptoms is wide; fatigue and pain may not always be the prominent disabling features at initial presentation.
- Patients may have been investigated extensively, without positive findings, for varied physical symptoms and may feel frustrated by the lack of help received from the medical profession by the time the diagnosis is made.
- Cognitive difficulties represent a common and debilitating feature of ME. These difficulties manifest as self-reported problems with attention, memory and concentration, presenting objectively as slowed information processing speed particularly on complex tasks requiring sustained attention.
- Symptoms tend to vary in intensity and type over a period of weeks or months (and may evolve into what is more clearly ME with time), leading to uncertainty for both the patient and clinician about the course and nature of the underlying problem.
- None of the current diagnostic methods has been adequately tested to identify patients with ME when diagnostic uncertainty exists.
- ME cannot be diagnosed by any test currently available.
- The lack of consensus on how recovery should be defined or interpreted has also generated controversy and confusion.
Various definitions are used In order to make a diagnosis of ME; however, it is usual for a patient to satisfy the following diagnostic criteria: Severe fatigue for longer than six months, and at least four of the following symptoms:
- Headache of new type, pattern, or severity.
- Multi-joint pain without swelling or erythema.
- Muscle pain.
- Post-exertional malaise for longer than 24 hours.
- Significant impairment in short-term memory or concentration.
- Sore throat.
- Tender lymph nodes.
- Unrefreshing sleep.
An International Consensus in 2011 considered that the label ‘chronic fatigue syndrome’ had persisted for many years because of the lack of knowledge of the aetiological agents and the disease process. In view of more recent research and clinical experience that strongly pointed to widespread inflammation and multisystemic neuropathology, it was considered to be more appropriate and correct to use the term ‘myalgic encephalomyelitis’ (ME) because this indicates an underlying pathophysiology. This term will be used throughout this article. The criteria used for ME in adults included:
- Post-exertional neuro-immune exhaustion.
- Neurocognitive impairments.
- Neurosensory, perceptual and motor disturbances.
- Immune, gastrointestinal and genitourinary impairments.
- Energy production/transportation impairments.
The US Institute of Medicine has proposed that a new clinical entity – systemic exercise intolerance disease (SEID) – should replace the clinical entities ME and CFS. Until consensus is finally reached on terminology, we have chosen to use ME throughout our articles where appropriate.
There is a significant reduction in activity levels with an inability to return to normal function. ME is a fluctuating condition and symptoms can vary constantly and unpredictably both in nature and severity. Typical features include:
- The defining clinical feature of ME is post-exertional malaise (PEM), which is an exacerbation of symptoms that can follow even minor physical or mental exertion. There is often a delayed impact, lasting days or weeks before function is restored. PEM can also trigger a relapse.
- Activity-induced muscle fatigue precipitated by trivially small exertion (physical or mental) relative to the patient’s previous activity
- Cognitive dysfunction: problems with short-term memory, concentration, word-finding;
- Sleep problems – sleeping too little or too much, vivid dreams, unrefreshing sleep.
- Ongoing flu-like symptoms: including sore throats and enlarged glands, fever-like sweats, lethargy.
- Orthostatic intolerance: problems with pulse and blood pressure control leading to feeling faint/dizzy when upright.
Other common symptoms include:
- Pain, which can involve muscle, joints and nerves.
- Problems with balance and with temperature control.
- Sensitivity to light and sound.
- Alcohol intolerance.
- Gastrointestinal symptoms – eg, abdominal pain, bloating, diarrhoea.
There is a wide spectrum of severity. About 25% of people are severely affected.
- Mild: the patient is mobile and can care for themself and do light housework with difficulty.
- Moderate: the patient has reduced mobility and is restricted in all activities of daily living. They have usually stopped work or education. There is poor sleep quality and duration.
- Severe: the patient is unable to do anything for themself. They are housebound or bed-bound and often need a wheelchair if they can mobilise.
ME can lead to atypical seizures, speech and swallowing difficulties and extreme intolerance to light and sound. Those people affected to this degree will tend to be bed-bound, require continuous 24-hour care and may require tube-feeding.
ME is diagnosed following careful assessment of history, examination and exclusion of other possible causes of the presenting symptoms. There are currently no blood or other diagnostic tests available.
Many people with ME suffer prolonged delays before getting properly assessed and diagnosed. A number of people diagnosed as having ME do in fact have a different condition.
The differential diagnoses are many and varied. They will vary from patient to patient, depending on the initial presentation. See also the separate Fatigue and TATT article.
- Postural tachycardia syndrome (PoTS).
- Hypothyroidism, diabetes and anaemia should be considered as causes of fatigue.
- Systemic lupus erythematosus, rheumatoid arthritis and inflammatory bowel disease should be considered as causes of arthralgia.
- Underlying neoplasia should be considered as a cause of lymphadenopathy.
- Metabolic muscle disorders and myopathies should be considered as a cause of muscle pain and weakness.
- Psychiatric illness should be considered as a cause of depression and anxiety.
- Cardiological or respiratory causes should be considered for shortness of breath and chest pain, and many other illnesses, depending on the specific symptoms.
There is no currently available biomedical test which can be used to diagnose ME and it remains a diagnosis of exclusion. A full medical and psychosocial history and a thorough physical and mental state examination are essential.
In a patient in whom the diagnosis is suspected, the laboratory investigations performed are those required to rule out other causes of illnesses which may mimic ME, such as:
- Renal function and electrolytes, LFTs, TFTs.
- FBC, serum ferritin, ESR or plasma viscosity.
- Blood glucose.
- Test for gluten sensitivity.
- Antinuclear antibodies, rheumatoid factor.
- Creatine kinase.
- Urinalysis for protein, blood and glucose.
Reconsider the diagnosis if the patient does not have:
- Post-exercise fatigue
- Cognitive problems
- Sleep disturbance
- Chronic pain
There is currently no curative treatment but medications can be used to help manage or control some symptoms, such as pain and sleep disturbance.
The most important aspect of ongoing care is activity management. This involves striking the right balance between activity and rest so as not to exacerbate symptoms. This is called pacing.
Activity needs to be gradually increased within any individual’s limitations and symptom fluctuations. The initial tendency to get into a cycle of excessive activity (such as going back to work) followed by further time off from work through ill health. This reduces the chance of any meaningful improvement. Therefore specialist involvement is needed at an early stage, including physiotherapy and occupational therapy.
Some people find complementary therapies such as acupuncture useful for ME, but there are many unsubstantiated ‘miracle cures’.
The current NICE guideline has not been updated since 2007 and continues to be very controversial. The ME Association has long regarded these guidelines as unfit for purpose, particularly because of the inclusion of two controversial therapies: graded exercise therapy (GET) and cognitive behavioural therapy (CBT). Many patients have found these therapies to be very detrimental.
Some studies have reported that CBT and GET are effective treatments for ME. However, one study found that there may be similar or poorer outcomes when used in routine clinical practice.
Some studies have shown that, although CBT may bring about changes in self-reported fatigue for some patients in the short term, there is a lack of evidence for long-term benefit or for improving physical function, indicating that CBT may cause distress if used inappropriately.
The management of ME is therefore very controversial and it is considered by some that CBT and GET may not only be ineffective and not evidence-based but also potentially harmful for many people with ME.
The issue of CBT being used as a therapy on the basis of the idea that ME is essentially a psychological illness that may well be triggered but is then perpetuated by abnormal illness beliefs and abnormal illness behaviour is an approach that many patients find both inappropriate and offensive. The NICE guideline is currently being reviewed.
The outcome is very variable and there is currently no effective method for predicting how the illness will progress or whether it will improve or resolve for any individual patient.
- A significant minority remain permanently and severely affected and many will see fluctuations in severity over a period, with some getting progressively worse.
- Some patients recover to the extent that they are able to continue virtually normal activities, with periodic ME symptoms.
- Lower recovery rates and higher relapse rates are associated with those who have had ME for many years.
- Children can be very severely afflicted but those whose symptoms are of mild-to-moderate severity are generally more likely than adults to go into remission.
- Chronic Fatigue Syndrome/Myalgic Encephalomyelitis – A Primer for Clinical Practitioners; International Association for Chronic Fatigue Syndrome/Myalgic Encephalomyelitis
- Newly diagnosed with M.E./CFS – information and advice for you and your GP; Action for ME
- Geraghty KJ, Esmail A; Chronic fatigue syndrome: is the biopsychosocial model responsible for patient dissatisfaction and harm? Br J Gen Pract. 2016 Aug66(649):437-8. doi: 10.3399/bjgp16X686473.
- The ME Association
- Bested AC, Marshall LM; Review of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: an evidence-based approach to diagnosis and management by clinicians. Rev Environ Health. 201530(4):223-49. doi: 10.1515/reveh-2015-0026.
- Committee on the Diagnostic Criteria for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome; Board on the Health of Select Populations Institute of Medicine
- Nacul LC, Lacerda EM, Pheby D, et al; Prevalence of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) in three regions of England: a repeated cross-sectional study in primary care. BMC Med. 2011 Jul 289:91. doi: 10.1186/1741-7015-9-91.
- Crawley E; The epidemiology of chronic fatigue syndrome/myalgic encephalitis in children. Arch Dis Child. 2014 Feb99(2):171-4. doi: 10.1136/archdischild-2012-302156. Epub 2013 Oct 21.
- Cvejic E, Birch RC, Vollmer-Conna U; Cognitive Dysfunction in Chronic Fatigue Syndrome: a Review of Recent Evidence. Curr Rheumatol Rep. 2016 May18(5):24. doi: 10.1007/s11926-016-0577-9.
- Haney E, Smith ME, McDonagh M, et al; Diagnostic Methods for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Systematic Review for a National Institutes of Health Pathways to Prevention Workshop. Ann Intern Med. 2015 Jun 16162(12):834-40. doi: 10.7326/M15-0443.
- Adamowicz JL, Caikauskaite I, Friedberg F; Defining recovery in chronic fatigue syndrome: a critical review. Qual Life Res. 2014 Nov23(9):2407-16. doi: 10.1007/s11136-014-0705-9. Epub 2014 May 3.
- Yancey JR, Thomas SM; Chronic fatigue syndrome: diagnosis and treatment. Am Fam Physician. 2012 Oct 1586(8):741-6.
- Carruthers BM, van de Sande MI, De Meirleir KL, et al; Myalgic encephalomyelitis: International Consensus Criteria. J Intern Med. 2011 Oct270(4):327-38. doi: 10.1111/j.1365-2796.2011.02428.x. Epub 2011 Aug 22.
- Twisk FN; Replacing Myalgic Encephalomyelitis and Chronic Fatigue Syndrome with Systemic Exercise Intolerance Disease Is Not the Way forward. Diagnostics (Basel). 2016 Feb 56(1). pii: E10. doi: 10.3390/diagnostics6010010.
- Chronic fatigue syndrome/Myalgic encephalomyelitis (or encephalopathy) diagnosis and management; NICE Clinical Guideline (August 2007)
- Fernie BA, Murphy G, Wells A, et al; Treatment Outcome and Metacognitive Change in CBT and GET for Chronic Fatigue Syndrome. Behav Cogn Psychother. 2016 Jul44(4):397-409. doi: 10.1017/S135246581500017X. Epub 2015 Apr 21.
- Geraghty KJ, Blease C; Cognitive behavioural therapy in the treatment of chronic fatigue syndrome: A narrative review on efficacy and informed consent. J Health Psychol. 2016 Sep 15. pii: 1359105316667798.
- Twisk FN, Maes M; A review on cognitive behavorial therapy (CBT) and graded exercise therapy (GET) in myalgic encephalomyelitis (ME) / chronic fatigue syndrome (CFS): CBT/GET is not only ineffective and not evidence-based, but also potentially harmful for many patients with ME/CFS. Neuro Endocrinol Lett. 200930(3):284-99.