PoTS and Chronic Fatigue Syndrome (ME/CFS) in Children: What Is the Difference?

PoTS and ME/CFS (myalgic encephalomyelitis / chronic fatigue syndrome) share many features and can look very similar from the outside. Both cause significant fatigue, cognitive difficulties and brain fog, and both are more common in adolescent girls. Both can follow a viral illness and they sometimes occur together in the same child. As a paediatric cardiologist, my role is to identify and treat the cardiovascular component and to recognise when ME/CFS may also be present so that the right referrals and adjustments can be made.

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What each condition is

PoTS is a cardiovascular condition. The heart rate rises excessively on standing because of disordered autonomic regulation of blood flow. Symptoms are primarily positional: worse when upright, better when lying down. This can be confirmed objectively with an active standing test, which gives PoTS a clear physiological basis.

ME/CFS is a complex multisystem condition that falls outside the scope of paediatric cardiology to manage directly. Its defining feature is post-exertional malaise (PEM): a worsening of symptoms, sometimes delayed by 12 to 48 hours, following physical or mental effort that would previously have been routine. This is not ordinary tiredness after exercise. It is a pathological response to exertion, and it is the feature that most clearly distinguishes ME/CFS from PoTS.

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Why the distinction matters

Structured graded exercise reconditioning is one of the most effective treatments for PoTS. It improves cardiovascular fitness, expands blood volume, and over weeks and months substantially reduces the compensatory tachycardia that defines the condition.

In ME/CFS, the same approach is not appropriate. The revised NICE guidelines published in 2021 are explicit that graded exercise therapy should not be recommended where post-exertional malaise is present, as it can cause significant worsening. This is one of the most practically important reasons to identify possible ME/CFS before starting any exercise programme for PoTS.

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When both may be present

The two conditions coexist in a significant proportion of patients, particularly following viral triggers including COVID-19 and glandular fever. Where I identify features suggesting both conditions, I address the cardiovascular component through fluid and salt supplementation, compression garments, and medication where appropriate. For the ME/CFS component, I refer to colleagues with expertise in that area, most commonly a paediatrician with a specialist interest in ME/CFS or a dedicated fatigue clinic, rather than attempting to manage it within a cardiology framework.

Where hypermobility is also present, the picture can be more complex and coordinated care across specialties becomes particularly important.

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How I approach this in clinic

In every child presenting with significant fatigue alongside orthostatic symptoms, I look specifically for features that might suggest ME/CFS. The key questions are around post-exertional malaise: does physical or mental activity reliably cause a delayed deterioration? Is there a pattern of crashes that goes beyond ordinary tiredness? Where those features are present, the management plan is adjusted and onward referral arranged. The PoTS component can still be treated effectively. The two diagnoses are not mutually exclusive, and a child who is functionally limited should not have to wait for diagnostic certainty before receiving active support.

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Author: Dr. Alessandro Giardini, MD, PhD, Consultant Paediatric Cardiologist

Written 11/06/2026