Does the rs9273363 AA genotype mark increased autoimmune thyroid disease susceptibility?

The claim is supported: rs9273363 AA can mark an HLA class II genetic background linked to autoimmune thyroid disease susceptibility, but it is an indirect, ancestry-dependent marker rather than a diagnostic or predictive genotype.

Genetic and clinical association

• rs9273363 lies near HLA-DQB1 in the MHC class II region. In reported African-American data, the A allele had complete linkage disequilibrium by D′ (1.00) with both DR3-DQ2 and DR4-DQ8, but modest correlation (r² 0.43 and 0.23, respectively). Thus, AA indicates an HLA-DR/DQ presentation background but cannot identify which classical risk haplotype is present.
• Particular class II haplotypes are associated with autoimmune thyroid disease, not class II variation uniformly. In Graves disease, HLA-DQA105:01 was associated with increased risk (OR 2.29, 95% CI 1.76–2.97) and DQA103:01 with a smaller increase (OR 1.30, 95% CI 1.03–1.63); DR3-DQ2 commonly confers roughly two- to threefold risk in European-ancestry populations.
• For Hashimoto thyroiditis, DRB104–DQB103–DQA103 was associated with increased risk (OR 1.98, 95% CI 1.51–2.59). Conversely, DQA102:01 was protective for Graves disease (OR 0.47, 95% CI 0.32–0.69).

Mechanistic interpretation

• HLA-DR/DQ molecules shape presentation of thyroglobulin and thyroid-peroxidase peptides to CD4+ T cells, potentially enabling autoreactive T- and B-cell responses. Linked peptide-binding variation—such as DQB1 position 57 and DRB1 positions 13 and 71—may be more biologically relevant than rs9273363 itself.

Clinical implications

• Bottom line: AA at rs9273363 supports a population-specific inference of HLA-mediated autoimmune-thyroid susceptibility, but does not predict whether this 57-year-old man will develop Graves disease or Hashimoto thyroiditis. Classical HLA typing/imputation would be needed for specificity, and routine HLA testing is not recommended for screening or prediction.