DRESS syndrome in a patient with rheumatoid arthritis: Navigating the intersection of drug-induced hypersensitivity and immune-mediated inflammation

Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a highly severe drug-induced hypersensitivity reaction with significant morbidity. Its diagnosis can be particularly challenging in patients with autoimmune diseases receiving multiple medications. We present the case of a woman in her late 30s with recently diagnosed rheumatoid arthritis and hyperthyroidism who developed high-grade fever, diffuse rash and facial oedema following treatment with allopurinol, leflunomide and carbimazole. Her symptoms were attributed to DRESS syndrome, supported by findings of eosinophilia, hepatic involvement and positive autoantibodies, and confirmed by skin biopsy. Discontinuation of the suspected offending drugs and initiation of anti-inflammatory therapy led to complete clinical resolution. This case highlights the complexity of diagnosing DRESS syndrome in patients with autoimmune conditions, the need to differentiate drug hypersensitivity from autoimmune disease flares and the importance of prompt intervention for optimal outcomes.