Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)
Exam Tips
- NICE-style diagnosis is clinical: in adults, suspect after at least 6 weeks of core symptoms and confirm after persistence for about 3 months once alternative diagnoses are excluded.
- Post-exertional malaise is the discriminating feature in OSCE/viva cases; simple tiredness without delayed crash is less suggestive.
- State severity by function (mild/moderate/severe/very severe) because this drives management intensity and safeguarding needs.
- A common exam pitfall is proposing rigid graded exercise escalation; current UK guidance emphasizes individualized pacing and symptom-contingent activity.
- Explain flare-up (shorter, transient worsening) versus relapse (more sustained deterioration requiring longer-term energy-plan adjustment).
Definition
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a chronic, fluctuating, multisystem condition diagnosed clinically by a characteristic symptom pattern rather than a single biomarker. It is defined by disabling fatigue with post-exertional symptom exacerbation, unrefreshing sleep, and cognitive dysfunction, causing substantial functional impairment that is not explained by another condition.
Pathophysiology
ME/CFS is thought to arise from interacting biological systems rather than one lesion: immune dysregulation (including post-infectious immune activation), autonomic dysfunction (for example orthostatic intolerance), altered neuroendocrine stress responses, and impaired cellular energy metabolism. A useful model is a lowered 'energy envelope' in which even minor physical or cognitive effort triggers post-exertional malaise via abnormal recovery physiology; central sensitization may also contribute to pain, sensory hypersensitivity, and sleep disturbance. Triggers commonly include viral illness (for example EBV or SARS-CoV-2), but persistence is likely maintained by a complex brain-body network dysfunction rather than ongoing tissue destruction.
Risk Factors
- Female sex
- Preceding infection (for example infectious mononucleosis, COVID-19, Lyme disease)
- History of overexertion or prolonged stress around onset
- Sleep disturbance
- Physical trauma or major illness as a trigger
- Possible genetic susceptibility (evidence not yet definitive)
Clinical Features
Symptoms
- Debilitating fatigue, disproportionate to activity and not relieved by rest
- Post-exertional malaise (worsening after physical, cognitive, or emotional effort, often delayed and prolonged)
- Unrefreshing or disturbed sleep
- Cognitive dysfunction ('brain fog': poor concentration, slowed processing, memory difficulties)
- Orthostatic intolerance symptoms (light-headedness, palpitations, presyncope)
- Myalgia, arthralgia, headaches, and flu-like malaise
- Sensory hypersensitivity (light, sound, touch)
- Fluctuating pattern with flare-ups and possible longer relapses
Signs
- Often few specific examination signs despite marked disability
- Reduced functional capacity on routine activity history
- Possible postural tachycardia or blood pressure instability on standing
- Sleep deprivation features and psychomotor slowing
- In severe disease: marked mobility limitation, wheelchair dependence, or bedbound state
Investigations
Management
Lifestyle Modifications
- Validate diagnosis and provide clear explanation of fluctuating course and post-exertional malaise
- Individualized energy management ('pacing') to stay within current energy limits and reduce crashes
- Do not prescribe fixed graded exercise therapy programmes that require progressive activity increases despite symptoms
- Sleep routine optimization, symptom diary, and structured activity-rest planning
- Education/work adjustments, social support, and occupational therapy input
- Nutritional support and hydration; in severe/very severe cases, home-based care with sensory-load minimization
Pharmacological Treatment
Simple analgesia for pain/headache
- Paracetamol 1 g orally every 4-6 hours when required (maximum 4 g/day)
- Ibuprofen 200-400 mg orally up to three times daily with food (prescription doses may be higher; use lowest effective dose)
Symptom relief only; no disease-modifying drug exists. Avoid or use caution with NSAIDs in chronic kidney disease, peptic ulcer disease, heart failure, anticoagulant use, and late pregnancy.
Neuropathic-pain or sleep-modulating options (specialist/individualized use)
- Amitriptyline 10 mg at night, titrating gradually (for example to 25-50 mg at night if tolerated)
Off-label in many ME/CFS scenarios; start low and titrate slowly due to hypersensitivity to adverse effects. Avoid in significant QT-prolongation risk, acute mania, severe liver disease, and use caution with anticholinergic burden or overdose risk.
Orthostatic intolerance/POTS-associated symptoms (if present, often specialist-led)
- Fludrocortisone 100 micrograms daily (titrate cautiously)
- Midodrine 2.5 mg two to three times daily, last dose at least 4 hours before bed
Use only when non-pharmacological measures are insufficient. Monitor blood pressure/electrolytes with fludrocortisone; avoid midodrine in severe organic heart disease, acute kidney disease, urinary retention, or thyrotoxicosis because of supine hypertension risk.
Comorbid mood disorders
- Sertraline 50 mg once daily, increase in 50 mg steps at intervals of at least 1 week to usual range 50-200 mg daily
Treat depression/anxiety when diagnostic criteria are met; this does not treat core ME/CFS pathology. Counsel about early GI effects, sleep change, and suicidal ideation monitoring, especially in younger people.
Complications
- Severe long-term disability (including housebound or bedbound states)
- Educational and occupational loss, including inability to sustain full-time work
- Social isolation, stigma, and disengagement from healthcare
- Comorbid anxiety and depression
- Deconditioning and worsening orthostatic intolerance
- Increased risk of self-harm/suicide in some cohorts
Prognosis
Course is typically chronic, fluctuating, and unpredictable, with variable outcomes between individuals. Available cohort data suggest a minority achieve full recovery (often quoted around 5-20%), many experience partial improvement over time, and a substantial subgroup remains significantly impaired long-term; pain-predominant or multi-symptom phenotypes are associated with poorer short-term outcomes.
Sources & References
🏥BMJ Best Practice(1)
✅NICE Guidelines(1)
📖Textbook References(3)
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1071)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1071)[context]
- [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 878)[context]