Clustering of autoimmune disease in parents of siblings from the Type 1 diabetes Warren repository

Aims Autoimmune disorders co‐exist in the same individuals and in families, implying a shared aetiology. The aim of this study was to compare the prevalence of the common autoimmune diseases in the parents of siblings from the Type 1 diabetes Warren repository with the general population. Methods Between 1989 and 1996, 505 British families with at least two siblings affected by Type 1 diabetes were recruited. Clinical information was collected regarding the presence of autoimmune disease in the parents and the prevalence of disease in the parents was compared with that expected in the general population. Results The prevalence of autoimmune disease in the parents was significantly higher in the repository compared with that expected in the general population [P‐value = 1.98 × 10−5 (female), P‐value = 1.1 × 10−8 (male)]. Type 1 diabetes was recorded in 63/1010 (6.2%) parents with a marked paternal preponderance (9.5 vs. 3%P = 0.002). Other autoimmune diseases affected 27% of parents with diabetes and 13.2% of parents without diabetes (P