Autoimmune thyroid disease in inborn errors of immunity: a retrospective perspective

Autoimmune thyroid diseases (AITDs) are among the most frequently reported autoimmune manifestations in individuals with inborn errors of immunity (IEIs). While immune dysregulation in IEI is known to predispose patients to autoimmunity, data regarding the prevalence and characteristics of AITD in this population remain limited. This study aimed to assess the frequency of AITD and describe its clinical, serological, ultrasonographic, and immunological features in a cohort of adult IEI patients. This retrospective study included 45 adult IEI patients, excluding those with selective IgA deficiency. Demographic, clinical, and immunological data were collected from medical records. AITD diagnosis was based on thyroid-specific autoantibodies, thyroid function tests, and/or ultrasonographic features consistent with thyroiditis. Comparative analyses were conducted between patients with and without AITD. AITD was identified in 7 patients (15.5%), including 6 with Hashimoto’s thyroiditis (HT) and 1 with seronegative chronic autoimmune thyroiditis (SN-CAT); no cases of Graves’ disease were observed. The majority of patients with AITD were female (85.7%), while only one case occurred in a male (14.3%). No statistically significant sex-based difference in AITD frequency was detected (p = 0.225). Anti-thyroid peroxidase antibodies were positive in 85.7% of AITD patients, and anti-thyroglobulin antibodies in 60.0%. All were euthyroid at evaluation, though 57.1% were receiving L-thyroxine therapy. Non-AITD thyroid abnormalities were present in 12 patients (26.6%), including isolated serology and a solitary thyroid nodule. Compared with non-AITD patients, those with AITD exhibited significantly higher CD16⁺56⁺ NK cell percentages (p = 0.010), while other lymphocyte subsets did not differ. No significant differences were observed regarding sex, IEI phenotype, non-thyroidal autoimmunity, or infection-related complications. In this adult IEI cohort, HT was the most prevalent autoimmune thyroid condition. Distinct immunological features, particularly increased NK cell frequencies, may reflect underlying immune dysregulation. These findings support systematic thyroid evaluation, even in asymptomatic IEI patients, and emphasize the need for larger, genetically diverse cohorts to validate and expand these observations.