1. epidemiology The prevalence of fulminant type 1 diabetes mellitus is not fully understood, and it has been reported that the incidence is higher in yellow than in white, with the highest incidence in Japanese, accounting for about 15-20% of type 1 diabetes mellitus [1]. Zhou Zhiguang et al [2] reported that there were 5 cases of fulminant type 1 diabetes among 144 patients with type 1 diabetes in this hospital, accounting for about 2.8%. Among other Asians, it has been reported in both Koreans and Filipinos. Previously, few cases have been reported in Europe and the United States, but three cases have been reported in France in recent years [3]. Imagawa et al [1] found that fulminant type 1 diabetes can develop at any age, with a higher average age of onset than type 1A diabetes. The odds of onset were almost equal in men and women, and the age of onset was (35.1 ± 15.8) years in female patients, significantly lower than (42.8 ± 14.8) years in men, which may be associated with a higher incidence in pregnant women. The mean body mass index (BMI) at onset was (20.7±3.9) kg/m2, significantly higher than that of (18.8±2.8) kg/m2 in type 1 diabetes. the disease appeared to have the highest incidence in May, but there was no significant difference compared to other seasons. There was no significant difference in family history of diabetes mellitus in patients with fulminant type 1 diabetes compared to type 1A diabetes mellitus. Fulminant type 1 diabetes is significantly associated with pregnancy [4], mostly immediately after delivery or 3 months after delivery.A study by Imagawa et al [1] demonstrated that almost all type 1 diabetes with onset during pregnancy is fulminant type 1 diabetes, and 2l% of fulminant type 1 diabetes in women of childbearing age 13-49 years was associated with pregnancy. This study also found that the chance of developing type 1A diabetes during pregnancy is small. 2. Pathogenesis 2.1 Genetic susceptibility Some studies have shown that human leukocyte-associated antigen type II (HLA II) gene polymorphisms are associated with the development of FDM, that increased frequency of certain genotypes on HLA DR-DQ may be correlated with FDM, and that the frequency of DR4-DQ4 is significantly increased in FDM. DR4-DQ4 is a common susceptibility gene for FDM and autoimmune type 1 diabetes, but DR9-DQ3 is not a susceptibility gene for FDM, and this difference may be one of the reasons why they have different pathogenesis. One study reported that a pair of Korean twin brothers had the same HLA DR-DQ haplotype [5] but different phenotypes, i.e., FDM and autoimmune type 1 diabetes, respectively. It is suggested that other factors besides genetic susceptibility may be at play in the development of FDM, such as viral infections. 2.2 Viral infections Viruses associated with FDM have been found to include herpes virus, coxsackievirus, and echovirus, the latter two being enteroviruses [6].Shimada [7] et al. reported that intraperitoneal injection of encephalomyocarditis virus (EMC-virus) caused clinical features similar to human FDM in experimental mice. A national survey from Japan showed that 71.2% of patients with FDM had flu-like symptoms at the beginning of the disease, and some patients had significantly higher titers of enterovirus IgA antibodies [1]. A statistically significant increase in serum enterovirus IgA antibody titers was reported in 19 patients with FDM, compared with normal controls and autoimmune type 1 diabetes group [8]. However, FDM does not occur in every individual infected with enterovirus, suggesting that viral infection is only one relevant factor in the development of FDM, in which there is also a genetic susceptibility. It is currently thought that FDM may occur as a result of viral infection on the basis of genetic susceptibility, but the exact pathogenesis is unknown. It has been reported in the literature that pancreatic tissue biopsies performed in five patients with FDM revealed minimal residual pancreatic islet B cells and a significantly reduced number of alpha cells, no evidence of isletitis in pancreatic tissue, and no Fas/Fas ligand expression; whereas autoimmune type l diabetes is a specific immune response against pancreatic cells, and there is autoimmune isletitis with a large infiltration of lymphocytes and monocytes, with Fas/Fas ligand expression, without islet alpha cell involvement [9]. It is evident that the pathogenesis of FDM differs significantly from that of autoimmune type 1 diabetes. It has been reported that 98% of patients with FDM have transient elevated pancreatic enzymes at the onset of the disease [1]. Pancreatic tissue biopsies have also confirmed the presence of lymphocytic infiltration in the exocrine pancreas in all patients with FDM, but without the manifestations of acute pancreatitis such as edema, hemorrhage, and necrosis [10,11]. This indicates that patients with FDM have not only destruction of the endocrine part of the pancreas, but also involvement of the exocrine part. 2.3 Immune response In 2000, Imagawa et al [1] reported that 11 patients with FDM had negative islet autoantibodies, so it was assumed that FDM was not related to autoimmunity, while later they found that about 4.8% of FDM patients were positive for glutamic acid decarboxylase antibodies in a nationwide survey in Japan, but with low titers and short duration; Tanaka et al [10] reported that a case of FDM who died suddenly Tanaka et al [10] reported that an autopsy done in a patient with sudden death of FDM revealed lymphocytic infiltration in both the internal and external secretory parts of the pancreas, so some scholars believe that there may be factors of autoimmune response involved in the pathogenesis of FDM. In summary, viruses may destroy pancreatic β-cells through the following 3 pathways: (1) viruses directly infect β-cells in susceptible individuals and self-replicate intracellularly leading to cell destruction; (2) viral infection activates the intrinsic immune response and removes the virus and infected β-cells through the action of macrophages, in which cytokines and nitric oxide pathways may play an important role; (3) the adaptive immune response is activated Since both endocrine and exocrine parts of the pancreas are involved in FDM and there is no manifestation of autoimmune isletitis, the second pathway may be the main pathogenesis. Clinical observation also revealed that some patients with FDM have abnormal liver function and viral encephalitis, indicating that FDM may be caused by a systemic nonspecific inflammatory response that mainly involves the pancreas. The diagnosis of fulminant type 1 diabetes should have the following 3 points: (1) development of ketosis or ketoacidosis within l week of the onset of hyperglycemic symptoms; (2) blood glucose ≥16.0 mmol/L and HbA1c <8< span="">.5% at the first visit; (3) fasting C-peptide <0.3ng/ml (100pmol/L) and post-stimulation (postprandial or glucagon) C-peptide < 0.5ng/ml(170pmol/L)