Juvenile idiopathic arthritis: Case

Framing the case

This three-year-old girl has the classic presentation of the oligoarticular juvenile idiopathic arthritis with the chronic anterior uveitis. The swollen knee for ten weeks, the morning stiffness that improves with activity, the single joint, the antinuclear-antibody positivity and the cells and the flare on the slit-lamp together make the diagnosis, and the framework that organises the case is the ILAR classification, the persistent-versus-extended split, the uveitis risk profile and the stepwise treat-to-target care. The first priority is the management of the uveitis and the joint, and the exclusion of the septic-arthritis mimic. ^[1][2]

Classifying and risk-stratifying the disease

The ILAR classification requires the arthritis of one or more joints for at least six weeks in a child under sixteen with the other causes excluded, and this child meets the criteria with the ten-week duration. She has one joint in the first six months, which assigns her to the oligoarticular category, the commonest subtype at about half to two-thirds of the cases. The oligoarticular disease splits at the six-month mark into the persistent, where the disease stays in four joints or fewer, and the extended, where further joints become involved after the first six months, and the split will be determined at the six-month review. The uveitis risk is the highest in the oligoarticular subtype, and she meets all four of the high-risk criteria: she is young, antinuclear-antibody positive, oligoarticular and within the first four years of the disease. ^[1][9]