Infection of an urachal cyst during etanercept therapy in juvenile idiopathic arthritis.

Etanercept, a tumor necrosis factor (TNF) receptor alpha antagonist is licensed for the treatment in patients affected by polyarticular juvenile idiopathic arthritis, who do not tolerate or had an inadequate response to methotrexate. Infections related to immunosuppression by etanercept are of major concern. We report on a 17-year-old boy with enthesitis-related arthritis who developed a major infection of an urachal cyst 18 months after initiation of etanercept therapy, which required surgery. The urachus had not been symptomatic before.