ME/CFS – myalgic encephalomyelitis/chronic fatigue syndrome – is one of the most debated and most misunderstood conditions in paediatric medicine. For years, it sat at the intersection of uncertain biology, contested treatment, and stigma: children and families who reported severe fatigue that didn't improve with activity were sometimes told that the problem was psychological and the solution was pushing through. The evidence and the clinical guidance have moved significantly, and the 2021 NICE guideline reflects a substantially better understanding of why that approach was harmful.
None of this means the condition is straightforward. Diagnosis, management, and prognosis are still complex. But the starting point – that this is a real, serious, and biologically rooted condition – is now supported by the clinical guidance, even if the precise mechanisms remain under investigation.
Healthbooq (healthbooq.com/apps/healthbooq-kids) covers complex chronic conditions in children.
What ME/CFS Is
ME/CFS is defined by a cluster of symptoms, not by a specific biomarker or test result. The core diagnostic criteria (based on the Institute of Medicine's 2015 report, which informed the NICE 2021 guideline) require all three of the following:
A substantial reduction or impairment in the ability to engage in pre-illness levels of educational, social, or personal activities, present for more than 6 months.
Post-exertional malaise (PEM): a worsening of symptoms following physical or cognitive exertion, which may be delayed (often 12-48 hours after the activity) and is out of proportion to the exertion. PEM is the most diagnostically distinctive feature and is what makes graduated exercise potentially harmful.
Unrefreshing sleep.
And at least one of: cognitive impairment (difficulties with memory, concentration, and processing speed, sometimes described as "brain fog") or orthostatic intolerance (worsening of symptoms when upright, including POTS-type symptoms of dizziness, nausea, and accelerated heart rate on standing).
How Common It Is and What Causes It
ME/CFS affects an estimated 25,000-50,000 children and young people in the UK, according to Action for ME. It can occur at any age from primary school onwards; the peak incidence in children is in the early-to-mid teenage years.
The condition is often triggered by infection. Glandular fever (Epstein-Barr virus) is the most commonly identified trigger: around 10% of people with glandular fever develop post-infectious fatigue meeting ME/CFS criteria. Enteroviruses, COVID-19 (long COVID overlaps substantially with ME/CFS in its symptom profile and mechanisms), and other acute infections have all been documented as triggers.
Why most people recover from infection and some develop ME/CFS is not understood. Research into immune dysregulation, mitochondrial dysfunction, autonomic nervous system abnormalities, and neuroinflammation is ongoing. Studies by teams at University College London, King's College London (including work by Trudie Chalder and the broader CFS/ME Research Collaborative), and internationally at Columbia University (Ian Lipkin) have documented measurable biological abnormalities including altered immune activation, metabolic abnormalities, and autonomic dysfunction – refuting the idea that the condition is primarily psychological in origin.
Recognising ME/CFS in Children
The diagnosis is clinical and requires the exclusion of other conditions that could explain the symptoms. A reasonable investigation panel at diagnosis includes: full blood count, renal and liver function, thyroid function, inflammatory markers (ESR, CRP), coeliac screen, random glucose, and vitamin B12 and D. These investigations are to exclude treatable conditions, not to look for a marker of ME/CFS.
The key feature that clinicians are looking for is PEM – not just fatigue, but the characteristic worsening after exertion. Many children with ME/CFS have tried to push through their fatigue at some point (often on the advice of well-meaning adults) and have experienced significant relapse; this history is diagnostically important.
The cognitive symptoms are often underappreciated: a child who is struggling to concentrate, who is slower to process information, who has difficulty holding multiple pieces of information in mind simultaneously, may be seen as not trying or as anxious rather than as cognitively impaired by their illness.
The NICE 2021 Guideline and the Shift in Management
The 2021 NICE guideline on ME/CFS was a significant event in the history of the condition. It removed graded exercise therapy (GET) and the Lightning Process from the list of recommended treatments. GET had been a standard recommendation for many years, based on the premise that deconditioning and fear of activity were central to the perpetuation of symptoms, and that graduated increases in exercise would reverse this. The evidence from long-term follow-up and patient surveys, including analyses by researchers at King's College London, documented that a substantial proportion of people with ME/CFS who had GET reported being made worse, not better, particularly those with significant PEM.
The current recommended approach is:
Energy management (pacing): Working within the available energy envelope rather than pushing through it. The goal is to identify the activity level at which symptoms don't worsen and to build a stable baseline from there, rather than oscillating between too much activity and prolonged crashes. Pacing is the most important skill for someone with ME/CFS to develop; specialist physiotherapy that understands this approach is more helpful than standard physiotherapy.
Sleep management: Sleep is typically non-restorative in ME/CFS and sleep architecture is often disturbed. Avoiding sleeping in the day (which worsens nocturnal sleep), maintaining consistent sleep and wake times, and, where needed, short-term pharmacological support under medical guidance, are aspects of sleep management.
Orthostatic intolerance management: Hydration, salt intake, and, in more severe cases, compression garments and medication (fludrocortisone, beta-blockers) for confirmed POTS, can reduce the functional impact of orthostatic symptoms.
School and education: Most children with ME/CFS cannot sustain full-time school attendance during the acute phase. A graded return to school – starting with whatever is manageable and not causing significant PEM – is supported by educational adjustments. Most schools can provide reduced timetables, rest facilities, and extended deadlines. An EHC plan may be appropriate for those with significant and prolonged impact on education.
Prognosis
The prognosis in children and adolescents is generally better than in adults: around 60-70% of children with ME/CFS are significantly improved or recovered at 5-year follow-up, though this varies considerably with severity. Children with milder presentations do better than those with severe ME/CFS who are largely housebound or bedbound. Long-COVID-related ME/CFS has introduced a new and large cohort whose prognosis is still being established.
Action for ME and the ME Association are the main UK charities providing support, information, and advocacy for affected families.
Key Takeaways
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex, multi-system condition characterised by profound fatigue that is not explained by other diagnoses, worsened by physical or mental exertion, and typically associated with post-exertional malaise, sleep disturbance, cognitive difficulties, and orthostatic intolerance. It affects an estimated 25,000-50,000 children in the UK. The cause is unknown but is often triggered by infection. NICE published new guidelines in 2021 that removed graded exercise therapy (GET) as a recommended treatment after evidence that it can worsen the condition; management now centres on energy management (pacing), symptom control, and education support. The condition is contested in some clinical and scientific quarters, but the lived experience of affected children and families is not.
