Thymus variants on imaging in patients with rheumatoid arthritis - Clinical and immunological significance

Objectives: We sought to clarify the presence of radiographic thymus variants using a scoring system, and their association with clinical and immunological features in RA patients. Methods: A total of 387 RA patients were randomly selected from all patients visiting our department who underwent chest CT scanning, with exclusion of patients with thymoma or thymic cyst, or age < 30 years. Thymus size and attenuation score in axial CT images were quantitatively interpreted and assessed. Associations between immunophenotype data and clinical and serological features were analysed in a subset of patients. Results: Thymic enlargement was found in 76 (19.6%) patients, and a thymus attenuation score ≥ 2 was found in 50 (12.9%) patients. The score was significantly associated with antibodies to ACPA positivity. Thymic enlargement was significantly associated with the proportions of CD4+ effector memory T cells. Conclusion: Radiographic thymus variants were frequently observed in RA patients and may reflect an abnormal immune response involved in the pathogenesis of RA.