Kwashiorkor is a childhood disease caused by severe malnutrition - which, at the time of its naming in 1935 had a mortality rate of 90%.
It's known to be associated with a lack of protein intake in food. And has also been linked to aflatoxins (fungal toxins) which might be causing the associated liver damage.
Despite more than 80 years of research, the exact biomedical pathways which lead to the condition are unknown.
See: Kwashiorkor is still not fully understood Bulletin of the World Health Organisation. Volume: 81, Issue: 12