Post-exertional symptom exacerbation

Post-exertional symptom exacerbation or PESE is a significant increase in ME/CFS symptoms caused by over-exertion, which begins either immediately or may be delayed by hours or days. PESE involves a mix of symptoms, for example exhaustion, acute flu-like symptoms, pain and worsening of other ME/CFS symptoms.

Definitions
Post-exertional symptom exacerbation is defined in a number of different ways:
 * The International Consensus Criteria (2011) refer to PESE as one of several required symptoms of post-exertional neuroimmune exhaustion (PENE), defined as "post-exertional exhaustion may occur immediately after activity or be delayed by hours or days."
 * The UK's NICE ME/CFS diagnostic criteria 2021 (NG206) refer to it as an alternative name for post-exertional malaise (PEM).

Prevalence
When listed as a separate diagnostic criteria, post-exertional symptom exacerbation is a mandatory symptom that is required for ME/CFS to be diagnosed.