Thymus variants were frequently observed in patients with rheumatoid arthritis (RA) and were associated with immunological and serological features of an abnormal immune system response, according to study results published in Rheumatology.
Thymic abnormalities have been observed in patients with systemic autoimmune diseases such as myasthenia gravis and systemic sclerosis and have been associated with the presence of autoantibodies in these conditions, the researchers acknowledged. This study was conducted to identify radiographic thymus variants in patients with RA and evaluate the association of these variants with clinical and immunological features.
Patients with RA who were aged 30 and older and had undergone chest computed tomography (CT) scanning from January 2013 to December 2015 were randomly selected from all patients visiting the Division of Rheumatology at Keio University Hospital in Tokyo, Japan. The thymus was measured and scored from 0 (predominantly fat tissue) to 3 (predominantly solid tissue). Enlargement was defined as greater than 13 mm in thickness. In a subset of patients, thymic enlargement and score were compared with immunophenotype data and clinical and serological features.
Of the 387 patients evaluated, 76 (19.6%) had an enlarged thymus and 50 (12.9%) had a thymus attenuation score of 2 or 3. Using multivariate logistic regression analysis, the thymus attenuation score was found to be significantly associated with antibodies to citrullinated peptide antigens positivity (odds ratio [OR], 15.2; 95% CI, 1.38-167.8; P =.026). Thymic enlargement was significantly associated with high proportions of CD4+ effector memory T cells (P =.0094).
Limitations of the study were that it included patients undergoing treatment for RA, which may induce thymus changes, and it did not evaluate enlargement of secondary lymphoid tissues besides the thymus.
“The prevalence of both thymic enlargement and thymus attenuation score was higher in RA patients than in the general populations in the previous reports,” the researchers concluded. “Radiographic thymus variants may reflect an abnormal immune response involved in the pathogenesis of RA.”
Disclosure: This research was supported by Takeda Pharmaceuticals. Please see the original reference for a full list of disclosures.
Murata O, Suzuki K, Sugiura H, et al. Thymus variants on imaging in patients with rheumatoid arthritis — clinical and immunological significance. Rheumatology (Oxford). Published online February 16, 2021. doi:10.1093/rheumatology/keab164