No association between rheumatoid arthritis and insulin dependent diabetes mellitus: an epidemiologic and...

To acquire more information on the controversial question of a possible association between rheumatoid arthritis (RA) and insulin dependent diabetes mellitus we searched for insulin dependent diabetes mellitus among patients hospitalized due to RA in 2 rheumatism hospitals in Finland. Nine subjects with insulin dependent diabetes mellitus were found among an annual number of 1460 patients admitted to one of the hospitals due to RA. These figures give a frequency of insulin dependent diabetes mellitus in patients with RA of 0.6% (95% confidence interval 0.2-1.0%), which does not exceed the prevalence of insulin dependent diabetes mellitus among the middle aged population of Finland in general (0.5-0.6%). Accordingly, no overrepresentation of homozygosity for HLA-DR4 was found among the total number of 25 patients with RA as well as insulin dependent diabetes mellitus, though the opposite might be expected as these diseases have a common DR4 association--RA with DR4 and DR1 and insulin dependent diabetes mellitus with DR4 and DR3. Instead, an increased frequency of DR1 (p less than 0.0002) and the antigen combination DR1/4 (p less than 0.01) was found in the subjects with both RA and insulin dependent diabetes mellitus compared with the subjects with insulin dependent diabetes mellitus alone.