post-exertional malaise (PEM)
A key diagnostic feature of the disease ME/CFS. Post-exertional malaise is a disease response to exertion and distinguishes ME/CFS from other fatigue-related disorders.
According to the ME/CFS research and treatment clinic the Bateman Horne Center, PEM refers to a significant worsening of symptoms and functional decline following physical, cognitive, or emotional exertion that would have been tolerable before illness onset.
The Bateman Horne Center lists several characteristics of PEM describing a trigger and a crash state:
- Triggers of crash symptoms are unpredictable, in response to minimal exertion, and can include sensory triggers such as light and sound or environmental stressors.
- Crash symptoms are delayed in onset, appearing 12 to 48 hours after the triggering activity.
- A severity and duration of crash symptoms disproportionate to the trigger.
- A prolonged recovery from the trigger during which the patient experience experiences intensified crash symptoms lasting days to weeks.
On first instance, use post-exertional malaise, also known as PEM. On subsequent uses, use PEM. The abbreviation code is: <abbr title="post-exertional malaise">PEM</abbr>.
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