Can we always be certain if certain symptoms seen in someone with such as ME/CFS reflect a distinct bit cooccurring condition are a down stream consequence of the ME/CFS?
I have IBS type symptoms that appear as part of PEM. These symptoms largely vary with my ME so are they part of my ME or do I also have concurrent IBS. I did have an episode of IBS symptoms associated with salmonella poisoning around a decade before my ME onset, but they did not reappear until after that onset. However, since my ME started I have also developed food intolerances which also trigger IBS type symptoms. Subjectively I feel my IBS type symptoms are ME symptoms rather than an additional condition, but one could argue the other way.
Similarly my food intolerances seem to post date my ME onset; are they part of the ME, are they a separate condition triggered by the ME, are they a down stream consequence of having ME resulting for change in diet or a sedentary lifestyle or are they purely coincidental? They post date my ME and the symptoms they trigger overlap my ME symptoms, their impact like PEM is delayed, with gluten by 24 hours, however they do not seem to vary with my current ME status, for example any response to gluten depends on the quantity of any gluten containing food consumed not my current ME severity. Subjectively it feels my food intolerances are now distinct to my ME, but I feel they were somehow triggered by my ME.
One could go through similar discussions about migraines, orthostatic issues, autonomic issues, vitamin deficiencies, frequent urination, perhaps even depression.
For many years I needed to urinate more frequently when in PEM, but reverted to normal when out of PEM. However as I become an old man, I have developed the old man condition of benign enlarged prostrate, and my need to urinate now seems primarily impacted by my prostate and its treatment, to the extent that any impact of PEM is not noticeable. Here the simplest explanation is probably that whatever the previous impact of my ME, my current prostate issues are not directly related to my ME, but can I be sure it was not a trigger.
Because of the length of time people have ME, because of the variation in symptoms and because of the non specific nature of many ME/CFS symptoms and because the multiplicity of our symptoms it may be until we understand its biological underpinnings they will be a distinct grey area around what the relationships between ME/CFS and presumed cooccurring conditions are.