Simultaneous onset of type 1 diabetes in monozygotic twins younger than 1 year.

This report describes type 1 insulin deficient diabetes mellitus (IDDM) arising in identical twins aged under one year. One twin presented with symptoms and was diagnosed with type 1 IDDM; the diagnosis of type 1 IDDM was simultaneously made in the second twin without clinical symptoms. Both twins were positive for anti-GAD (glutamic acid decarboxylase) antibody at first, and then positive for islet cell antibodies. Interestingly, the twins have four susceptible HLA DR and DQ genes together that are usually recognized separately in IDDM patients in Japan.