Thymic enlargement in a patient with juvenile idiopathic arthritis during etanercept therapy

Tumor necrosis factor (TNF) alpha inhibitors are effective in the treatment of inflammatory rheumatic diseases. Despite their effectiveness, anti-TNF drugs have some drawbacks such as severe adverse effects including infections and possibly lymphoproliferative disorders. In this report we described a case of juvenile idiopathic arthritis patient who developed thymic enlargement (true thymic hyperplasia), mediastinal lymphadenopathy and pleurisy associated with systemic symptoms under Etanercept treatment. The clinical presentation was highly suggestive of malignancy and the patient underwent diagnostic mediastinoscopy with biopsy.