Abstract
A family with prevalent islet-cell surface antibodies (ICSA) and type I diabetes mellitus is reported. Four of the five members studied, mother, monozygotic male twins and sister, were positive for circulating ICSA/IgG, but none had anti-islet cell cytoplasmic antibodies (ICA). Two of them (mother and twin proband) had overt insulin-dependent diabetes mellitus. The sister showed a diabetic glucose tolerance with no fasting hyperglycemia and with substantially diminished insulin secretion in both oral and iv glucose tests. One non-diabetic twin had modest glucose intolerance and beta-cell dysfunction, when examined by a 25g iv glucose challenge test. Therefore, these non-diabetic siblings apparently are at increased risk for the development of type I diabetes mellitus. No association was found between the ICSA positivity and any types of HLA that are characteristic of Japanese type I diabetes. However, the three siblings had an identical HLA type and the mother shared 3 HLA types with them. There is no evidence for autoimmune polyendocrinopathy in any members. This family may provide interesting insight into both the genetics and pathogenesis of type I diabetes mellitus.
