Clinical characteristics of non-immune-mediated, idiopathic type 1 (type 1B) diabetes mellitus in Japanese children and adolescents.

To clarify the characteristics of idiopathic type 1 (type 1B) diabetes mellitus (DM), we compared the clinical features of immune-mediated type 1 (type 1A) DM and type 1B DM in 85 Japanese children and adolescents with DM. The prevalence of type 1B DM was 16.5%. The patients with type 1B DM were significantly younger at diagnosis and had a higher frequency of preceding viral infection before onset, compared to those with type 1A DM. They displayed more severe metabolic decompensation with a higher frequency of ketoacidosis at diagnosis than patients with type 1A DM. They had strong, HLA-defined genetic susceptibility, similar to that in type 1A DM. Some patients with type 1B DM exhibited a remarkably abrupt onset and rapid loss of beta-cell capacity. From these findings, it is considered that type 1B DM differs from type 1A DM with respect to age at onset and the trigger event, such as viral infection, leading to rapid destruction of beta-cells without autoimmunity in the etiology of the disease.