 - Patients with a diagnosis of oligoarticular, polyarticular, psoriatic or enthesitis-related JIA as determined by ILAR criteria. Patients who have been continuously treated with generic sulfasalazine delayed release formulation and have tolerated the product for at least 3 months prior to study enrolment and who are switched to Azulfidine-EN at least 8 days prior to Day 0 are eligible. 