Enthesitis-related arthritis is a type of juvenile idiopathic arthritis (JIA) that represents the paediatric form of spondylarthropathy in adults. Its prevalence is estimated at 1-30 children in 66,000 with an annual incidence of 1-60 in 2,000,000 children. Around 70% of patients are male, with onset usually occurring between ages 10 and 12. In contrast to the clinical picture observed in adults, the initial manifestations in the paediatric form involve mainly the peripheral joints with asymmetric oligoarticular arthritis of the lower limbs, associated with pain in the tendon insertion zone (enthesitis). Axial manifestations (lumbar and buttock pain as a result of sacroiliac involvement) are present in only 25% of cases at onset but appear several years later in the disease course. The presence of a `sausage-like' finger or toe is a hallmark sign of inflammation of the interphalangeal joints and flexor tendon sheath. The biological features of the inflammatory syndrome are inconstant. The exact cause of the disease and its mode of transmission remain unknown. Extraarticular infection is sometimes reported as a triggering factor. There is also the association with the presence the human major histocompatibility antigen HLA-B27, but the role of this antigen in disease determination remains hypothetical. Although around 70% of patients test positive for HLA-B27, this finding is not conclusive for the diagnosis. The diagnostic criteria for the disease were established in 2001 at the last international meeting in Edmonton. According to these criteria, the disease is defined by the presence of enthesitis and arthritis, or by the presence of arthritis and at least two of the following: sacroiliac pain and/or spinal inflammation, acute anterior uveitis, presence of the HLA-B27 antigen, and a family history of uveitis, spondylarthropathy, or sacroiliitis with inflammatory enteropathy in a parent or first-degree relative. Exclusion criteria include the presence of psoriasis in the patient or a family history of psoriasis in a parent or first-degree relative, detection of Rheumatoid Factor IgM in two tests taken at a 3 month interval, and the presence of systemic arthritis in the patient. The differential diagnosis should include infectious arthritis and other inflammatory diseases, as well as haematooncologic diseases that may lead to arthritis (in particular, connective tissue diseases and acute leukaemia). Treatment is best managed by a centre specialised in paediatric rheumatology and revolves around administration of nonsteroidal anti-inflammatory agents (NSAIDS). Intraarticular infiltration of delayed-action corticoids (triamcinolone hexacetonide) administered under sedation or general anaesthesia (in children under 3 years of age) is required in case of persistent arthritis (presence of arthritis after 4-6 weeks of treatment with NSAIDS). The use of disease-modifying antirheumatic drugs (Salazopyrine or tumour necrosis factor (TNF)-alpha) is only recommended in severe cases that are refractory to other forms of treatment. The efficacy of these treatments has been tested in several comparative, mainly noncontrolled, studies. In around 40% of cases, the disease is nonprogressive in adulthood. In the remaining cases, the disease evolves into spondylarthritis and is associated with an increased risk of hip involvement (30% of cases). Ankylosis of the spine has been reported, but is clearly not a constant feature.
Last update: January 2007