Background & Aims: There is an elevated prevalence of celiac disease (CD) in family members (FMs) of CD patients, but most prior studies have been done on selected populations. Our aim was to determine the clinical, serologic, and genetic predictors of CD in FMs of a population-based cohort of index cases. Methods: Index cases from southeast Minnesota provided contact information for their first-degree relatives. FMs were examined for endomysial antibodies (EMAs), tissue transglutaminase antibodies (tTGAs), and HLA-DQ genotyping. Two questionnaires were applied, Bowel Disease Questionnaire and Short Form Health Survey. Intestinal biopsies were offered if there were any positive autoantibody or seronegative FMs with gastrointestinal symptoms and HLA-DQ at risk for CD. Results: We recruited 111 index cases that had 579 FMs, of whom 344 (59%) were investigated. The average screening rate among families was 65%. A positive tTGA test was found in 47 (14%), 33 with a positive EMA test. CD was diagnosed in 39 (21 males), with an estimated prevalence of 11% (λR = 16.1). All affected FMs carried the at-risk genotypes. Twenty-one (54%) had "silent" disease, most with severe intestinal villous atrophy. Carrying HLA-DQ2 (odds ratio, 16.1; 95% confidence interval, 2.1-123) and being a sibling (odds ratio, 2.5; 95% confidence interval, 1.1-5.8) are high-risk factors for CD. Conclusions: CD is more common in first-degree relatives than previously reported in the United States, with siblings having the greatest risk. There is male preponderance of new cases, and many had silent disease despite severe histologic injury. A more proactive case-finding strategy in FMs might improve the diagnostic rate of CD in North America.
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