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    Created in 2008, Phoenix Rising is the largest and oldest forum dedicated to furthering the understanding of and finding treatments for complex chronic illnesses such as chronic fatigue syndrome (ME/CFS), fibromyalgia (FM), long COVID, postural orthostatic tachycardia syndrome (POTS), mast cell activation syndrome (MCAS), and allied diseases.

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Senior Member
Midwest, USA
Hey PR,

Hope everyone is as safe as can be during these strange times. Wanted to ask a quick question on here, as I hold this board in high esteem for knowledge & experiences.

Recently, I sought a second opinion from a fairly highly regarded MCAS physician in MN, just to see if they think MCAS could be playing a role in my ME/CFS illness (as my ME/CFS doctor suspects). This doctor is Dr. Shanda Dorff, for reference if any others have seen. On my evaluation with Dr. Dorff, she expressed to me that in her medical opinion, MCAS could explain my 2-Day CPET results (that my ME/CFS doctor, Dr. Chheda advised to complete), showing a significant drop in oxygen consumption and metabolic responses on the 2nd day of testing. That surprised me. I just always assumed PEM & MCAS were not really related - that I knew of at least (?).

I'm just curious if any others have come across this possibility or have been told this from their doctors (that their PEM could be due to MCAS), who have been suspected of MCAS. I know there seems to be a lot of overlap between ME/CFS & MCAS and I hope in time, science can answer.

Thanks for any intel you may provide.


Senior Member
I just always assumed PEM & MCAS were not really related - that I knew of at least (?).
Most ppl. think PEM only occours in ME/CFS, but there are
at least OTS (Overtraining-Syndrome which affects usually Highclass Athletes), and MCAS where something similar like PEM (or better said PENE in case off MCAS) can be detected, who knows perhaps in few FMS cases, too.

Many here know this PEM study (participants where CFS/FM sufferers)


MCAS has some so called "phenotypes" that differ from the symptoms,
there are MCAS cases that get "allergic" to exercising if their mastcells release uncontrolled Cytokine unter load + stress. As far as I know, there are no criteria how to differentiate them from CFS PENE

There were some stories around a former elite gymnast and her problems with exercising since she developed MCAS, just amazing what she maked out off her disabilty:
https://blog.scope.org.uk/2016/06/24/natasha-coates-the-gymnast-who-is-allergic-to-exercise/ :thumbsup:
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