By quickly scrolling through the blog, "Energy Supplementation" section caught my attention. I already could see that the guy made a grave mistake there. Instead of meticulously compensating the activity of mitochondrial enzymes with the whole RDA spectrum of vitamins, including therapeutical quantities of B1, B3, and B7 coenzymes, he just sporadically included some stuff from here and there. Unfortunately, this is not enough to move the needle in terms of ATP yield. And without the sufficient levels of ATP, all other functions of the body go downhill. The speed of that decline is individual, sometimes it's mere months from onset to terminal. Most of the times, however, it's a multi-year struggle.
The second grave mistake is concentrating too much on secondary symptoms (inflammation, shortness of breath, blood-clotting, autoimmune) without adequately fixing the root cause (energy depletion) that caused all of them.
The third grave mistake is presented in section "Things that hurt" -> "Supplements" -> "Thiamine is a histamine liberator and DAO inhibitor", which means that the guy didn't use it at all. And this is the gravest mistake of them all. It's true that the thiamine may increase histamine levels for some individuals, but mitochondria cannot function without it, like at all. The reason for that is thiamine-activated enzymes that sit at the very start of OXPHOS pathway. Without sufficient levels of thiamine, those enzymes cannot work. As the result, nearly all parts of OXPHOS metabolic pathway become dysfunctional, lowering ATP yields even more.
(IMHO, this is what happens when a hacker incorrectly identifies a place to fix the bug and prefers to apply workarounds instead of fixing the root cause. In software, we always have a second chance, but in bioware - we may not have it at all.)
Returning to your question, the symptoms are very much like beri-beri and pellagra. The cause of death is likely to be a multi-organ failure which can be manifested either as a heart attack, hypertensive crisis, liver dysfunction, renal failure, brain damage, or a combination of those.
I am in touch with physicians and many people and we discovered many things that people are trying that are mentioned in the blog. TNF-a inhibitors, anti-histamines and diets. Plus, many of the supplements listed.
I much appreciate all the work on that blog and will give it a good read at some point.