Chronic fatigue and post-viral fatigue syndromes — branching viva

Stem

The examiner will test whether you can run a validating, function-first chronic-fatigue pathway under pressure — refusing both dismissal and over-treatment, and recognising post-exertional malaise as the clinical core. [1] [2]

Branch 1 — First presentation and the discriminating feature

Examiner: A 14-year-old has fatigue four months after confirmed EBV infection. She sleeps 11 hours and wakes unrefreshed, and crashes for two days after PE. What is the single most discriminating feature, and what is your working diagnosis? [1]

Strong answer: The discriminating feature is post-exertional malaise (PEM) — a delayed, disproportionate worsening 24 to 72 hours after exertion, with slow recovery — combined with unrefreshing sleep and substantial activity limitation. With a focused normal exclusion panel, the working diagnosis is chronic fatigue syndrome / myalgic encephalomyelitis (CFS/ME). PEM distinguishes it from deconditioning (no delayed crash) and from depression (anhedonia — loss of interest — whereas she wants to play sport but cannot). [1] [8]

Branch 2 — Diagnostic threshold and exclusion

Examiner: Her GP wants to wait six months before diagnosing. How do you respond, and how do you exclude mimics? [1]

Strong answer: The paediatric threshold is around three months, not the six-month adult criterion, because children's trajectories differ and a longer wait delays rehabilitation and entrenches school disengagement. She is well past the threshold. I exclude mimics with a single focused panel — full blood count, inflammatory markers, ferritin, B12/folate, vitamin D, biochemistry, thyroid function, coeliac serology with total IgA, glucose and urinalysis — then stop unless a red flag appears. I avoid an endless cascade, and I frame the normal results as reassuring that her body is healthy, not that nothing is wrong. [1]

Branch 3 — The function-first plan

Examiner: Walk me through your management. [2]

Strong answer: Validate the illness as a real, multi-system disease; explain PEM and the energy envelope; set shared functional goals (school, sleep, friends) — not a cure promise. Build energy management within the energy envelope: pacing, planned rest, smoothing the boom-and-bust, activity escalated only as tolerated with the young person controlling the pace. Add CBT targeting activity cycles, sleep, fear and mood — the FITNET trial showed internet-based CBT restored full school attendance in 75% versus 16% of usual care at six months, with no serious adverse events. Treat comorbid mood and orthostatic intolerance. Build a graded, school-led return-to-school plan. [2]

Branch 4 — The graded-exercise controversy

Examiner: Her father wants her to "push through" with a structured exercise programme. Defend your position. [4]

Strong answer: Rigid, fixed-dose graded exercise therapy (GET) is not appropriate in CFS/ME with PEM. The adult PACE trial suggested CBT and GET helped, but it used the broad Oxford criteria, weakened its recovery criteria mid-trial, and patient organisations reported harm. The Cochrane review found exercise probably reduces fatigue versus passive controls but with very-low-certainty evidence on harm, and noted all included studies used Oxford or 1994 CDC criteria — patients with PEM may respond very differently. NICE NG206 (2021) withdrew fixed-dose GET. The synthesis is individualised, energy-envelope-based activity escalated only as tolerated, with the patient in control — not "push-through". [3] [4]

Branch 5 — Red-flag challenge

Examiner: Eight months in she reports new weight loss and night sweats. How does this change your plan? [1]

Strong answer: These are red flags that override a functional frame. Re-enter the diagnostic pathway with targeted investigation — inflammatory markers, LDH, directed imaging, considering malignancy and inflammatory illness — and reassess for organic disease. The pitfall is diagnostic overshadowing: attributing new symptoms to the CFS/ME label rather than investigating them on their merits. Document explicitly that new red flags are reassessed on their own terms, and tell the family. Do not abandon the function-first plan if organic disease is again excluded, but never let a functional label stop you thinking. [1]

Branch 6 — School absence and prognosis

Examiner: She is attending school only two days a week. Her mother asks whether she will ever recover. [6]

Strong answer: Treat school absence as a clinical outcome and a primary treatment target, not a coping choice — prolonged absence entrenches isolation, academic failure and depression and worsens prognosis. Build a graded, school-led return-to-school plan with education liaison. On prognosis, the evidence is hard to interpret: Moore and Crawley found recovery rates from 4.5% to 83% reflecting inconsistent definitions. What is defensible is that most children and adolescents improve substantially, and many recover fully, with early function-focused care; recovery is gradual over months to years. Delayed diagnosis, prolonged school disengagement, untreated mood disorder and rigid over-exertion worsen outcome. [6]

Examiner extras

• PEM is the clinical core — say it early and define it precisely. [1]
• The paediatric threshold is three months, not six. [1]
• Validate the illness as real; the encounter itself is therapeutic. [1]
• Fixed-dose graded exercise is out; individualised energy-envelope activity is in. [4]
• School reintegration is a clinical outcome, not an administrative detail. [6]
• Never let a functional label stop you from investigating a new red flag. [1]