Juvenile idiopathic arthritis is frequently misdiagnosed or diagnosed late because persistent joint pain in young children can seem improbable and because the early symptoms — joint stiffness, swelling, and a limp that is worse in the morning — can look like normal developmental growing pains or a sports injury. Children rarely describe "pain" in the arthritic sense; they more often stop using a limb, have an unexplained limp, or seem stiff and reluctant to move after rest.
One of the most serious complications — uveitis — causes no symptoms at all in the early stages. It is an inflammation of the middle layer of the eye that can silently damage vision for months before it is detected, which is why eye screening at three-to-six monthly intervals is a non-negotiable part of JIA care, particularly in certain high-risk subtypes.
Healthbooq (healthbooq.com) covers children's health through the early years.
What JIA Is
Juvenile idiopathic arthritis is not a single disease but a classification of arthritis in children under 16 that persists for at least six weeks and has no identifiable cause. The word "idiopathic" means the cause is unknown. JIA is not the childhood equivalent of rheumatoid arthritis in most subtypes — it has distinct patterns, triggers, and outcomes.
The International League of Associations for Rheumatology (ILAR) classifies JIA into seven subtypes based on the pattern of joint involvement, the presence or absence of systemic features, and laboratory findings including rheumatoid factor and antinuclear antibodies (ANA).
The Main Subtypes
Oligoarticular JIA (persistent) is the most common, accounting for around 50 per cent of JIA in the UK. Four or fewer joints are affected, typically large joints (knee, ankle, wrist). It predominantly affects young girls, often ANA-positive. This subtype carries the highest risk of uveitis — up to 30 per cent of children develop eye inflammation.
Polyarticular JIA (rheumatoid factor negative) affects five or more joints. It also predominantly affects girls and often involves smaller joints of the hands and feet as well as large joints.
Polyarticular JIA (rheumatoid factor positive) resembles adult rheumatoid arthritis and carries a worse prognosis. It tends to affect older girls and is associated with more erosive joint damage.
Systemic JIA (Still's disease) is characterised by prominent systemic features: a daily spiking fever, a salmon-coloured rash, lymphadenopathy, and hepatosplenomegaly, alongside arthritis. It is equally common in boys and girls and can be difficult to distinguish from other febrile illnesses early on. A severe complication called macrophage activation syndrome (MAS) is potentially fatal and requires urgent recognition.
Enthesitis-related JIA and psoriatic JIA are the remaining less common subtypes.
Symptoms to Watch For
The classic presentation of JIA is morning stiffness that improves with movement — worse on waking and after rest, better after an hour or so of activity. This pattern is characteristic of inflammatory rather than mechanical joint problems. A child who limps first thing in the morning but improves through the day, or who seems reluctant to use their hands after sleep, should be assessed.
Affected joints may be swollen, warm, and tender but are often surprisingly not very painful — children adapt to low-grade persistent inflammation. A joint that appears swollen compared to the opposite side is always worth investigating.
Systemic JIA can present like a mystery febrile illness: daily or twice-daily fever spikes to 39°C or higher that resolve between episodes, an evanescent rash (appearing with the fever), and a very unwell child with high inflammatory markers.
Uveitis
Anterior uveitis in JIA is typically asymptomatic in the early stages — no redness, no pain, no change in visual acuity until significant damage has occurred. It is detected only by slit-lamp examination by an ophthalmologist. Children with oligoarticular JIA and ANA-positive polyarticular JIA are at highest risk, and require eye screening every three months in the early years of diagnosis, reducing to every six months as risk decreases.
Untreated uveitis causes cataracts, glaucoma, band keratopathy (calcium deposits across the cornea), and permanent visual impairment. Treated uveitis responds to topical steroids and, if persistent, systemic immunosuppression.
Treatment
NSAIDs (such as naproxen or ibuprofen) reduce inflammation and symptoms and are often first-line treatment. Intra-articular corticosteroid injections give targeted relief to individual inflamed joints and are a mainstay of oligoarticular JIA management; in children, these are usually done under sedation or general anaesthetic.
Methotrexate is the most widely used disease-modifying drug (DMARD) in JIA. It is taken once weekly, usually as a subcutaneous injection for better tolerability, and requires regular blood monitoring. Folic acid supplementation is given alongside to reduce side effects.
Biological therapies (anti-TNF agents such as etanercept, or IL-6 inhibitors such as tocilizumab for systemic JIA) are used when conventional treatment is insufficient. They have transformed outcomes for many children with JIA.
Physiotherapy is essential throughout to maintain joint range of movement, muscle strength, and function.
Prognosis
Many children with oligoarticular JIA achieve remission in adulthood. Polyarticular and systemic subtypes have more variable outcomes. With modern treatment, most children with JIA can participate in normal childhood activities including sport.
Key Takeaways
Juvenile idiopathic arthritis (JIA) is the most common chronic rheumatic condition in childhood, affecting approximately 1 in 1,000 children. It is an umbrella term covering several distinct subtypes, all characterised by persistent joint inflammation in children under 16 lasting more than six weeks. The most common subtype, oligoarticular JIA, typically affects four or fewer joints and carries a significant risk of uveitis — eye inflammation that can cause permanent visual damage if not detected early. Management involves specialist rheumatology care, physiotherapy, and often medications including NSAIDs, methotrexate, and biological therapies. Regular eye screening is mandatory for all children with JIA.
