Chronic Fatigue Syndrome

💤 Chronic Fatigue Syndrome (CFS), also known as Myalgic Encephalomyelitis (ME), is a chronic disorder characterised by debilitating fatigue not relieved by rest, with associated cognitive, sleep, and musculoskeletal symptoms. It is a diagnosis of exclusion and can be highly disabling.

📖 About

• Chronic condition with unexplained, persistent fatigue.
• Often underdiagnosed; prevalence estimated around 0.2–0.4% of population.
• Profound functional impact – affects work, education, and quality of life.

⚠️ Risk Factors

• Twice as common in females 👩‍🦰
• More frequent onset after age 40
• No clear racial predilection

🧬 Aetiology

• Unclear pathogenesis – thought to involve immune, endocrine, and autonomic dysfunction.
• Possible role of viral infections, immune dysregulation, and genetic susceptibility.
• Links with childhood trauma and psychosocial stressors.

🩺 Clinical (CDC Diagnostic Criteria)

Requires severe fatigue >6 months with ≥4 of the following:

• Post-exertional malaise (symptom flare after activity)
• Unrefreshing sleep 😴
• Impaired memory or concentration (“brain fog”)
• Myalgia (muscle pain)
• Polyarthralgia (joint pains, no inflammation)
• Sore throat
• Tender lymph nodes
• New or different headaches

🧾 Oxford Criteria

• Fatigue is the primary symptom with a clear onset.
• Fatigue is severe, disabling, affecting physical & mental functioning.
• Symptoms >6 months, present >50% of the time.
• Other symptoms: myalgia, mood disturbance, sleep disturbance.
• Excludes those with psychiatric disorders (schizophrenia, bipolar, substance abuse) or known organic causes of fatigue.

🧪 Diagnosis

• Clinical diagnosis after excluding other causes.
• Consider concurrent depression, anxiety, sleep disorders, and pain syndromes.
• No specific laboratory abnormalities.

🚩 Red Flags (suggest alternative diagnosis)

• Chest pain / suspected ischaemic heart disease
• Focal neurological deficits (suggest MS, stroke, etc.)
• Unexplained weight loss, SOB, or lymphadenopathy (malignancy/infection)
• Marked inflammatory arthritis or systemic signs

🔍 Investigations (to rule out mimics)

• Bloods: FBC, U&E, Mg, Phosphate, Calcium, LFTs, CRP/ESR, TFTs, glucose
• Urinalysis
• Coeliac screen (anti-endomysial/TTG antibodies)
• Rheumatology screen: RF, ANA if clinically indicated
• Consider HIV, hepatitis, Lyme disease where relevant
• Sleep study if OSA suspected

🧾 Differentials

• Endocrine: Addison’s disease, diabetes, thyroid disorders, Cushing’s.
• Haematology/Oncology: Anaemia, malignancy.
• Infectious: HIV, TB, chronic hepatitis, Lyme.
• Neurological: MS, Parkinson’s, narcolepsy, dementia.
• Psychiatric: Major depression, bipolar disorder, somatisation.
• Rheumatology: Polymyalgia rheumatica, RA, SLE, Sjögren’s, fibromyalgia.
• Other: Coeliac disease, sleep apnoea, heart failure, drug effects, vitamin deficiencies.

💊 Management

• Education & pacing: Balance rest and activity to avoid “crash & boom” cycle.
• CBT: Can help coping strategies and reduce distress.
• Graded exercise therapy (GET): controversial; some patients benefit, others worsen – NICE (2021) advises cautious, personalised activity programmes.
• Sleep hygiene: addressing insomnia and poor sleep quality.
• Pharmacotherapy: No curative drug; SSRIs, duloxetine or low-dose amitriptyline may help mood, pain, and sleep disturbance.
• Multidisciplinary approach: GP, occupational therapy, physiotherapy, psychology support.

📌 Key Teaching Pearls

• CFS is a diagnosis of exclusion – always rule out thyroid disease, anaemia, autoimmune conditions.
• Post-exertional malaise is the hallmark feature distinguishing it from depression or primary sleep disorders.
• Overlap with fibromyalgia is common; both are central sensitivity syndromes.
• Prognosis: variable – some improve, others remain chronically impaired.

📚 References

• Chronic Fatigue Syndrome – AAFP
• NICE Guideline NG206: ME/CFS (2021)