Transglutaminase antibodies and celiac disease in children with type 1 diabetes and in their family members

Objectives We set out to determine the prevalence of tissue transglutaminase antibodies (anti-tTG) and celiac disease (CD) in children with newly diagnosed type 1 diabetes (T1D) and their first-degree relatives (FDR). The hypothesis was that the individuals with both diabetes and CD form a distinct subgroup in terms of human leukocyte antigen (HLA) class II genetics, islet autoantibodies, and clinical characteristics at diabetes diagnosis. Subjects and methods This population-based observational study included 745 index children with T1D and their 2692 FDR from the Finnish Pediatric Diabetes Register. CD was ascertained by registers, patient records, and screening anti-tTG positive individuals for further testing. Results Among the index children, 4.8% had anti-tTG at diabetes diagnosis, and at the end of the study 3.2% had CD. Among the relatives, 2.9% had anti-tTG (4.8% mothers, 2.4% fathers, and 2.1% siblings), and 2.5% had CD (4.6% mothers, 2.1% fathers, and 1.4% siblings). Anti-tTG and CD associated with the HLA DR3-DQ2 haplotype. The usual female predominance of CD patients was observed in relatives (70%) but not among index children (46%). The index children with both diseases had a lower number of detectable islet autoantibodies than those with diabetes alone. Conclusions The children with double diagnosis differed from those with diabetes alone in HLA genetics, humoral islet autoimmunity directed against fewer antigens, and in the lack of usual female preponderance among CD patients. Compared with 61% of the anti-tTG positive relatives, only 36% of anti-tTG positive index children developed CD implicating transient anti-tTG positivity at diagnosis of T1D.