Juvenile rheumatoid arthritis (JRA) is a term used to describe arthritis in children under 16 years old that lasts at least 6 weeks. It can be classified into oligoarticular JRA which affects 4 or fewer joints, polyarticular JRA which affects 5 or more joints, and systemic JRA which is characterized by arthritis, fever, and rash. Left untreated, JRA can lead to joint damage, deformities, limited movement, and growth issues.