Monogenic Hashimoto thyroiditis associated with a variant in the thyroglobulin (TG) gene

Abstract

Background Risk of autoimmune thyroid disease (AITD) is strongly heritable. Multiple genes confer increased risk for AITD, but a monogenic origin has not yet been described. We studied a family with apparent autosomal dominant, early onset Hashimoto thyroiditis. Methods The family was enrolled in an IRB-approved protocol. Whole exome sequencing was used to study the proband and an affected sibling. The identified variant was studied in other family members by Sanger sequencing. Results We identified a previously unreported splice site variant in the thyroglobulin gene (TG c.1076-1G > C). This variant was confirmed in all affected family members who underwent testing, and also noted in one unaffected child. The variant is associated with exon 9 skipping, resulting in a novel in-frame variant transcript of TG. Conclusion We discovered a monogenic form of AITD associated with a splice site variant in the thyroglobulin gene. This finding raises questions about the origins of thyroid autoimmunity; possible explanations include increased immunogenicity of the mutated protein or thyroid toxicity with secondary development of anti-thyroid antibodies. Further study into the effects of this variant on thyroid function and thyroid autoimmunity are warranted.