Yes, had a young family member that died from a cytokine storm many years ago. No autopsy. Diagnosed as flu then pneumonia, coma/sepsis, organ failure, death in a very short amount of time.
No one else in the family has succumbed that way since.
Don’t know if genetic quirk or what.
In recent years, a really big suspect has become arsenic.
First of all, even a small exposure inhibits the immune system from detecting novel pathogens, allowing them to establish themselves. Then when they are detected, the immune system overreacts with the cytokine storm.
For this reason, though arsenic is quite common from water wells (USGS), the EPA prohibits it in drinking water greater than 10 ppb (parts per billion), a ridiculously small amount.
https://www.wired.com/2013/09/arsenic-nation/
However, this being said, all this shows is that arsenic can *artificially induce* a cytokine storm. It does not mean that arsenic is the only thing that can do it, or that it is even a frequent cause of cytokine storms.