Post-exertional malaise
Post-exertional malaise is one of the main symptoms of myalgic encephalomyelitis/chronic fatigue syndrome. PEM can be described as "a delayed and significant exacerbation of ME/CFS symptoms that always follows physical activity and often follows cognitive activity".
PEM is considered a cardinal symptom by a number of the different diagnostic criteria for ME/CFS, including the International Consensus Criteria. The Canadian Consensus Criteria does not consider PEM compulsory, rather it requires "post exertional malaise and/or fatigue". The National Academy of Medicine's Systemic Exertion Intolerance Disease criteria requires PEM. The Centers for Disease Control and Prevention use the SEID/IOM 2015 Diagnostic Criteria on its website's ME/CFS page and list PEM as a primary symptom.
