RESUMEN
Forty-one simplex and 6 multiplex families of Brazilian IDDM patients were studied by the indirect immunofluorescence technique to determine the prevalence of the following autoantibodies: islet cells (ICA), islet cells which fix complement (ICA-CF), thyroid microsomes (TMA), thyroglobulin (TGA), and gastric-parietal cells (PCA). A total of 54 IDDM patients belonging to two family groups were analyzed. A significantly higher frequency of ICA-CF and TMA was detected among the siblings from multiplex families than among those from simplex families (18.7% vs 1.7%). A prospective study of ICA-positive siblings was undertaken, and 2 who later became diabetic were found to be positive to both ICA and ICA-CF. The prevalence of islet-cell antibodies in these 54 Brazilian IDDM patients and their unaffected first-degree relatives from generally mixed groups suggest that the humoral autoimmune mechanisms of the disease are probably identical to those observed in other population of different ethnic backgrounds