I agree it's hard to speculate: perhaps malnutrition and cardiac failure; maybe sepsis. Here are some relevant links — Life-Threatening Malnutrition in Very S

I agree it's hard to speculate: perhaps malnutrition and cardiac failure; maybe sepsis. Here are some relevant links — Life-Threatening Malnutrition in Very Severe ME/CFS (2021) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8070213/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8070213/ Caring for the Patient with Severe or Very Severe Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (2021) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8544443/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8544443/ There are not many mortality studies and few ME patients have had comprehensive autopsies — Mortality in patients with myalgic encephalomyelitis and chronic fatigue syndrome (2016) https://www.tandfonline.com/doi/full/10.1080/21641846.2016.1236588 https://www.tandfonline.com/doi/full/10.1080/21641846.2016.1... Causes of Death Among Patients With Chronic Fatigue Syndrome (2007) https://www.tandfonline.com/doi/abs/10.1080/07399330600803766 https://www.tandfonline.com/doi/abs/10.1080/0739933060080376... Somewhat harrowing reading is Whitney Dafoe's account of becoming extremely severe — Extremely Severe ME/CFS—A Personal Account (2021) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8145314/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8145314/