Systemic juvenile idiopathic arthritis (sJIA) is a type of arthritis that primarily affects children. It is characterized by persistent joint inflammation, fever, and a rash. Unlike other forms of juvenile idiopathic arthritis, sJIA can also impact internal organs, making it a more complex condition. The exact cause of sJIA is unknown, but it is believed to involve an autoimmune response, where the body's immune system mistakenly attacks its own tissues. Treatment typically includes medications to reduce inflammation and manage symptoms, allowing affected children to lead more active lives.