Studies on the classification of diabetes mellitus diagnosed before the age of 30 in Japan.

Since 1976, 551 patients with diabetes discovered before the age of 30 have been treated in the Diabetes Center of Tokyo Women's Medical College. Among them, 198 were classified as insulin-dependent diabetes (IDDM), 237 as non-insulin-dependent diabetes (NIDDM), 12 were unclassified, and four were classified as other types. In patients with IDDM, the number of males was lower than that of females, 80 and 118 respectively. The number of patients discovered with NIDDM over the age of 25 was much higher in males than in females. To study the influence of family history, 148 probands were selected from the 551 diabetics according to age at onset of diabetes (under 20 years old) and present age (between 20 and 40 years old). At the interview, the number of first-degree relatives and the number of diabetics among them were recorded. Six out of 75 probands (8%) with IDDM had positive family histories for NIDDM and two of the 75 (3%) had positive family histories for IDDM, although 39 out of 73 probands (53%) with NIDDM had positive family histories for NIDDM alone. There was only a slight difference in the course of retinopathy between patients with IDDM and NIDDM.