Diabetes
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Previous studies suggest that after 6 years of discordance, identical twin pairs rarely become concordant for type I diabetes. With up to 39 years of follow-up from the onset of diabetes in the index twin, we determined how many discordant twins have evidence of beta-cell autoimmunity and how many develop overt diabetes. We longitudinally followed 23 pairs of identical twins (or triplets) that were selected from a total group of 30 pairs because they were discordant for type I diabetes when first ascertained. ⋯ Two-thirds (8 of 12) had evidence of beta-cell autoimmunity (persistently positive autoantibody levels) and/or first-phase insulin release less than the 1st percentile of control subjects. In summary, identical twins may develop diabetes after a prolonged period of discordance and approximately two-thirds of long-term discordant twins have evidence of persistent beta-cell autoimmunity and/or beta-cell damage. The concordance for beta-cell autoimmunity, therefore, is much higher than for overt diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)