Type 1 diabetes associated with Hashimoto's thyroiditis and juvenile rheumatoid arthritis: a case report with clinical and genetic investigations.

Autoimmune diseases are initiated by interaction between genetic and environmental factors and caused by the loss of immunologic tolerance to self-antigens. They cluster within families and individuals, but the aggregation in a triad is quite rare. We report a case of a young girl affected by three organ-specific autoimmune disorders, from which type 1 diabetes developed first, then Hashimoto's thyroiditis and juvenile rheumatoid arthritis were diagnosed. Hitherto unreported detailed genetic studies included genotyping of HLA class II, CTLA4, and PTPN22 gene regions. These genes have been associated with autoimmunity in general and some of their variants confer increased risk to all three diseases. Our results - with the limitation of reporting only on a single patient - contribute to the complex genetic background of these clustering organ-specific autoimmune diseases and the analysis of further similar cases might help to reveal how the major and minor genetic factors determine the individual clinical phenotype.