Chronic fatigue and post-viral fatigue syndromes — formative SAQs

SAQ 1 — 14-year-old with fatigue four months after glandular fever (10 marks)

A 14-year-old girl presents with four months of exhaustion after confirmed Epstein-Barr virus infection. She sleeps 11 hours and wakes unrefreshed, and describes a two-day "crash" after physical exertion. She is now attending school only half-days. Targeted bloods (full blood count, inflammatory markers, ferritin, thyroid function, coeliac serology, biochemistry) and examination are normal. She desperately wants to return to sport and friends. Her father believes she should "push through"; her mother fears a serious disease is being missed. ^{[1] [5]}

Questions

1. Outline your diagnostic reasoning, including the key clinical feature that distinguishes this presentation from deconditioning or depression, and the paediatric duration threshold. (4 marks) ^[1]
2. Describe the focused assessment that supports the diagnosis and excludes mimics, including the active stand test. (3 marks) ^[1]
3. Outline the function-first management plan, including the role of graded exercise. (3 marks) ^{[2] [4]}

Model answer

Diagnostic reasoning (4). The clinical picture is chronic fatigue syndrome / myalgic encephalomyelitis (CFS/ME). The cardinal distinguishing feature is post-exertional malaise (PEM) — a delayed (24-72 hour), disproportionate worsening after exertion with slow recovery — combined with unrefreshing sleep and substantial activity limitation, with mimics excluded. PEM distinguishes CFS/ME from pure deconditioning (which lacks the delayed crash) and from depression (which is marked by anhedonia — loss of interest — whereas this girl wants to play sport but cannot). The paediatric threshold is around three months, not the six-month adult criterion, so she is well past the diagnostic threshold. ^{[1] [8]}

Assessment (3). Take a fatigue and activity history (onset/trigger, trajectory, exacerbators including PEM, sleep quality, functional impact) embedded in a HEEADSSS adolescent interview; screen for mood and suicidality; use a two-week activity and sleep diary to objectify the boom-and-bust pattern. Examine growth, cardiovascular, respiratory, abdominal and neurological systems with a mental-state examination. Perform an active stand test (heart rate and blood pressure supine, then at 2, 5 and 10 minutes standing) to screen for orthostatic intolerance and postural tachycardia syndrome, which commonly coexist and are treatable. Confirm the focused blood exclusion is complete, and avoid a further cascade without a red flag. ^[1]

Function-first plan (3). Validate the illness as a real, multi-system disease and explain PEM and the energy envelope; set shared functional goals (school, sleep, friends) rather than a cure promise. Build energy management within the energy envelope — pacing, planned rest, smoothing the boom-and-bust cycle, activity escalated only as tolerated with the young person controlling the pace. Add CBT (FITNET showed internet-based CBT restored full school attendance in 75% versus 16% of usual care at six months, with no serious adverse events) targeting activity cycles, sleep, fear of worsening and mood. Treat comorbid mood and orthostatic intolerance. On graded exercise: current guidance withdrew fixed-dose graded exercise therapy because rigid targets trigger PEM; activity is individualised and energy-envelope-based, not a prescribed increment for all. Build a graded, school-led return-to-school plan with education liaison. ^{[2] [4]}