Prevalence of Various Systemic and Organ-Specific Autoimmune Markers in Addison’s Disease Patients Compared to Healthy Controls

<b>Background:</b> Addison's disease (AD) is a rare disorder that often develops in the context of autoimmune polyglandular syndromes. However, the prevalence of rheumatological autoimmune diseases and corresponding autoimmune markers in AD is poorly investigated. Therefore, the present study aims to explore systemic and organ-specific immune markers in a cohort of AD patients from a single tertiary endocrine center. <b>Material and methods</b>: In total, 43 adult AD patients and 31 controls were included in the study. 21-hydroxylase autoantibodies (21OHAb), glutamic acid decarboxylase autoantibodies (GADAbs), zinc transporter-8 autoantibodies (ZnT8Abs), antibodies against nuclear antigens (ANAs), autoantibodies against cyclic citrullinated peptides (CCPAbs), rheumatoid factors (RFs), IgG autoantibodies against cardiolipin (ACLAbs), and autoantibodies against beta-2-Glycoprotein I (β2-GPIAbs) were measured in all participants. <b>Results</b>: An increased prevalence of antibodies against RFs (27.91% vs. 0%, <i>p</i> < 0.001) and ANAs (13.95% vs. 0%, <i>p</i> = 0.037) was found in AD patients compared to controls. Moreover, the titers of 21-hydroxylase and RF antibodies correlated positively (r = +0.269, <i>p</i> = 0.020). The AD patients tended to show an increased prevalence of subthreshold ACL antibody reactivity compared to controls. All patients diagnosed with type 1 diabetes mellitus were GADAb- but not ZnT8Ab-positive. <b>Conclusions</b>: The results show an increased prevalence of ANA and RF positivity in AD patients compared to controls and a significant association between 21-OHAb and RF positivity. ZnT8Ab positivity was not typical for adult AD patients from our ethnic group, while GADAbs were an essential marker for autoimmune diabetes mellitus. Extensive studies in different ethnic groups are needed to establish the clinical significance of various immunological markers for AD comorbidity and the appropriate follow-up protocols for patients with different antibody positivity.