Fulminant type 1 diabetes is a new subtype of type 1 diabetes. The term was established in 2000. It is a syndrome characterized by a markedly rapid and almost complete destruction of pancreatic beta-cells. Several lines of evidence suggest that both genetic factors, such as human leukocyte antigen (HLA), and environmental factors, such as viral infection, contribute to the development of this disease. It is also suggested that autoimmune processes contribute less critically to fulminant type 1 diabetes than to classic type 1A diabetes. Based on the findings made to date, both viral infection and the subsequent immune reaction in genetically susceptible individuals cause beta-cell destruction and lead to fulminant type 1 diabetes.