Summary

Juvenile psoriatic arthritis is a relatively rare form of juvenile idiopathic arthritis (JIA) representing less than 10% of all JIA cases. Its prevalence has been estimated at between 1 and 10 children per 33,000 with an annual incidence of between 1 and 20 in 1,000,000. Psoriatic arthritis is a heterogeneous disease characterised by the association of psoriasis with one of two forms of arthritis: the association of psoriasis with an arthritis that most resembles oligoarticular arthritis with a risk of uveitis is more common in girls with onset at around 6 years of age, whereas the association of psoriasis with a form of arthritis that most resembles a spondylarthropathy is most common in boys and manifests later. Psoriatic arthritis is an autoimmune inflammatory disorder with hyperproduction of proinflammatory cytokines, most notably tumour necrosis factor (TNF)-alpha. The diagnostic criteria for the disease were established in established in 2001 at the last international meeting in Edmonton. According to these criteria, the disease is characterised by the presence of a form of arthritis and psoriasis, or by the presence of arthritis associated with at least one of the following signs: dactylitis, ungual pitting or onycholysis, and a familiy history of psoriasis in the parents or a first-degree relative. Exclusion criteria include: HLA B27-positivity in males with onset of arthritis after 6 years of age; detection of rheumatoid Factor IgM in two test samples taken three months apart; the presence of ankylosing spondylarthritis, enthesitis and arthritis, sacroiliitis with an inflammatory enteropathy or acute anterior uveitis in the patient or a family history or one of these conditions in a parent or first-degree relative; and the presence of systemic arthritis in the patient. The differential diagnosis includes other diseases associated with arthritis (infectious, inflammatory and haematooncologic diseases), in particular those associated with more common forms of arthritis or with cutaneous psoriasis that occurs after arthritis. Treatment is best managed in a specialised centre by a paediatric rheumatologist. As for other forms of JIA, treatment of psoriatic arthritis revolves around administration of non-steroidal anti-inflammatory agents (NSAIDS), in some cases associated with intraarticular injections of delayed-action corticoids (triamcinolone hexacetonide). The role of disease-modifying antirheumatic drugs (methotrexate or biotherapeutic agents) has not yet been firmly established. Depending on the case, the prognosis appears to be similar to that for patients with oligoarticular arthritis or enthesitis-related arthritis (see these terms) but as the disease is very rare, few studies have been performed.

Expert reviewer(s)

• Dr Chantal JOB DESLANDRE