Autosomal dominant Hashimoto's thyroiditis with a mutation in .

Hashimoto's thyroiditis (HT) is an autoimmune disease thought to involve a combination of genetic and environmental factors, but its detailed pathogenesis is unknown. We present a family with haploinsufficiency of the gene encoding tumor necrosis factor α-induced protein 3 (, also known as ) and show a link with HT in a three-generation pedigree. Currently, polymorphisms are associated with several autoimmune diseases, and haploinsufficiency of A20 was recently observed in families with an early-onset autoinflammatory disease resembling Behçet's disease. However, HT has not been linked with variants. We analyzed and human leukocyte antigen () in the family showing HT as an autosomal dominant trait, and identified a novel heterozygous c.2209delC mutation of in the members with HT. The known HLA haplotypes linked to HT could not be identified. Based on our analysis of this pedigree, we consider HT as a possible phenotype of A20 haploinsufficiency.