2 Clinical need and practice
2.1 Juvenile idiopathic arthritis (JIA) describes all forms of arthritis that have an unknown cause, an onset younger than 16 years, and joint inflammation that lasts more than 6 weeks. JIA is classified by the number of joints affected. Oligoarticular JIA, also known as oligoarthritis, is diagnosed when 4 or fewer joints are affected over the first 6 months after diagnosis. Polyarticular‑onset JIA, also known as polyarthritis, is diagnosed when 5 or more joints are affected over the first 6 months after diagnosis. After 6 months from diagnosis, if 5 or more joints become affected it is then referred to as polyarticular‑course JIA. This includes people who are diagnosed with oligoarticular JIA but who then have more joints affected after 6 months (also known as extended oligoarticular JIA). Other subtypes of JIA include systemic, enthesitis‑related and psoriatic arthritis. These can have additional symptoms or conditions including:
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systemic JIA: fever, tiredness, rash, loss of appetite and weight loss
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enthesitis‑related arthritis: affects entheses (where tendons attach to the bones)
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psoriatic arthritis: psoriasis.
People with enthesitis‑related and psoriatic arthritis can have polyarticular‑course JIA, as can people who initially had systemic JIA providing there have been no active systemic symptoms in the previous 6 months.
2.2 About 1000 children are diagnosed with JIA in the UK per year, and about 10,000 children have the condition. JIA may continue into adulthood, and about a third or more of children with the condition still need treatment in adult life.
2.3 At the onset of JIA, swollen and painful joints can limit movement. Later, progressive joint damage can permanently disable patients and it has been estimated that between 7% and 28% of patients need joint replacements. About 10–20% of patients with JIA (mainly those with systemic or polyarticular JIA who need high‑dose corticosteroids) have impaired growth. JIA can decrease bone mass and increase the risk of osteoporosis. It is associated with a range of extra‑articular manifestations, notably uveitis (inflammation of the middle layer of the eye); about 30–50% of children with JIA have uveitis at diagnosis. Untreated uveitis can be associated with cataracts, glaucoma and macular oedema, and about 50–70% of people with severe uveitis develop visual impairment. Children with JIA are screened for uveitis in England.
2.4 NICE issued technology appraisal guidance on the use of etanercept for the treatment of juvenile idiopathic arthritis in 2002. The recommendation states that 'etanercept is recommended for children aged 4 to 17 years who have active JIA in at least 5 joints and whose condition has not responded adequately to methotrexate or who have been unable to tolerate treatment with methotrexate'. This current multiple technology appraisal reviews this guidance because the marketing authorisation for etanercept now includes children from 2 years with polyarticular JIA, and children and young people with extended oligoarthritis, enthesitis‑related arthritis and psoriatic arthritis. Also, abatacept, adalimumab and tocilizumab have all got marketing authorisations for JIA since the previous guidance was issued. This multiple technology appraisal does not include people with systemic JIA because tocilizumab is the only intervention licensed to treat this type of JIA, and because there is already NICE technology appraisal guidance recommending tocilizumab for children and young people whose disease has failed to respond to methotrexate. Of note, people with systemic JIA may develop polyarticular‑course JIA (see section 2.1), which is covered by this multiple technology appraisal.