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.