The geoepidemiology of type 1 diabetes.

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by absolute insulin deficiency resulting from the progressive immune-mediated destruction of pancreatic islet beta cells. It is thought to be triggered by as yet unidentified environmental factors in genetically susceptible individuals, the major genetic contribution coming from loci within the HLA complex, in particular HLA class II. The worldwide incidence of T1D varies by at least 100-fold, being highest in Finland and Sardinia (Italy) and lowest in Venezuela and China. The incidence has been increasing worldwide at an annual rate of approximately 3%. While genetic factors are thought to explain some of the geographic variability in T1D occurrence, they cannot account for its rapidly increasing frequency. Instead, the declining proportion of newly diagnosed children with high-risk genotypes suggests that environmental pressures are now able to trigger T1D in genotypes that previously would not have developed the disease during childhood. Although comparisons between countries and regions with low and high-incidence rates have suggested that higher socioeconomic status and degree of urbanization are among the environmental factors that play a role in the rising incidence of T1D, the findings are too inconsistent to allow firm conclusions. Morbidity and mortality as well as causes of death also show considerable geographic variation. While glycemic control has been identified as a major predictor of the micro- and macrovascular complications of T1D and shows considerable geographical variability, it does not appear to be the only factor involved in the regional differences in complication rates. The role of genetics in susceptibility to nephropathy, retinopathy and other diabetic complications largely remains to be explored.

Antibodies to nucleic acids in congenital immune deficiency states.

The presence of antibodies to native DNA, single-stranded DNA, and double-stranded RNA was determined for 37 patients with selective IgA deficiency, 11 patients with Wiskott-Aldrich syndrome, seven patients with common variable agammaglobulinemia, 14 patients with ataxia telangiectasia, six patients with intestinal lymphangiectasia, and one patient with Nezelof syndrome. Of 37 patients with selective IgA deficiency, 11 had antibodies to at least one nucleic acid; six had antibodies to native DNA, seven had antibodies to single-stranded DNA, and four had antibodies to double-stranded RNA. The only other congenital immune deficiency disease studied in which antibodies to nucleic acids were found was the Wiskott-Aldrich syndrome; in this group three of 11 patients had antibodies to native DNA. Retrospective analysis of our patients with SLE disclosed a 2.6% prevalence of IgA deficiency, a prevalence clearly higher than in the general population. These studies provide further evidence of the association between autoimmunity and abnormalities of IgA production and suggest a relationship between thymic-derived immune regulation and IgA production.