Type 1 (insulin-dependent) diabetes mellitus with coexisting autoimmune thyroid disease in Japan

Type 1 diabetes mellitus is known to be a heterogenous disease which is frequently complicated with other autoimmune thyroid diseases (AITD). The present study was designed to investigate the clinical characteristics and HLA antigens in Japanese Type 1 diabetic patients with AITD. Subjects were 25 Type 1 diabetic patients with AITD (13 Graves' disease and 12 Hashimoto's thyroiditis) and 32 Type 1 diabetic patients without AITD. Compared with Type 1 diabetic patients without AITD, age at onset of diabetes was later and positive ICA persisted much longer in the diabetic patients with AITD. Compared with normal controls, DR9 was increased in the patients with AITD, while DR4 was increased in those without AITD. Type 1 diabetic patients with AITD were characterized by the late onset of diabetes, persistent ICA and increased association with DR9. These results suggest that immunological and genetic heterogeneity may exist within Japanese Type 1 diabetic patients.