I obviously can not with any certainty say that such a crash is not related to what I describe as PEM, but I would want to see some of the counter intuitive aspects, such as general malaise, swollen glands, delayed onset, a course of symptom worsening not simply correlated with rest, cross modality effects, new or dormant symptoms re-emerging etc, before I was confident in saying what is being described is ME/CFS type PEM. Though obviously unless we identify an underlying organic process we can not say these different experiences involve the same phenomenon or not.