Systemic-onset juvenile idiopathic arthritis is marked by the severity of the extra-articular manifestations (fever, cutaneous eruptions) and by an equal sex ratio. It represents 10-11% of cases of juvenile idiopathic arthritis (JIA). The prevalence has been estimated at 1-10 in 30,000 children with an annual incidence of 1-20 in 900,000 children. Onset usually occurs between 3 and 5 years of age. The clinical signs include fever with oscillating temperatures over a 24-hour period and peaks of over 39°C or more. These fever peaks are associated with transient cutaneous eruptions and diffuse erythematosis or urticarial-like lesions. The presence of arthritis is essential for diagnosis but may appear later in the disease course. The number of sites affected is variable (mono-, oligo- or polyarthritis) affecting both the small and large joints in a nearly symmetrical manner. This characteristic diagnostic triad may also be associated with an adenopathy and hepatosplenomegaly. Visceral complications (pericarditis, pleural effusion or serous peritonitis with abdominal pain) may be present. There are no specific biological signs but the inflammatory disease is severe with a large increase on the level of ferritin and a decrease in the percentage of glycosylated ferritin. The underlying mechanisms and triggering factors have not yet been identified, but the disease can be clearly distinguished from other forms of JIA. The disease may represent an autoimmune disorder rather than an autoinflammatory disease (as for periodic fever and CINCA/NOMID). The clinical triad of daily fever (lasting more than 2 weeks), arthritis and transient cutaneous eruptions is vital for diagnosis (criteria established at in 2001 at the last international meeting in Edmonton). In the absence of cutaneous eruptions, the presence of an adenopathy, hepatosplenomegaly or serous effusion also confirm the diagnosis. There is no specific biological sign. Exclusion criteria are the presence of systemic arthritis or psoriasis in the patient, or a family history of psoriasis in one of the parents or a first-degree relative, HLA B27-positivity in males with onset of arthritis after 6 years of age and detection of rheumatoid factor IgM in two test samples taken three months apart. Other exclusion criteria include: the presence of ankylosing spondylarthritis, enthesitis and arthritis, sacroiliitis with an inflammatory enteropathy or acute anterior uveitis in the patient or a family history of one of these conditions in a parent or first-degree relative. The differential diagnosis should include fever associated with infection, connective tissue disease (notably lupus), acute leukaemia and other autoinflammatory diseases. Management should be carried out at a specialised centre. High doses of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) constitute the first-line treatment. In cases refractory to treatment over a period of 2-6 weeks, high-dose corticotherapy should be used. Disease-modifying antirheumatic drugs (methotrexate and biotherapy) may be recommended in case of corticoresistance but their effectiveness varies. Other drug treatments (thalidomide, interlukin-1 receptor antagonists (anakinra) and monoclonal anti-interleukin-6 monoclonal antibody (MRA) therapy) are available or currently under investigation for corticoresistant patients. In certain cases, intraarticular injection may be proposed. The disease resolves before adulthood in around half of patients. In the remaining cases, the arthritis persists, with or without fever and cutaneous eruption. Severe sequelae are present in 20% of cases and involve growth delay, bone and cartilage erosion with functional handicap, and a risk of osteopaenia.
Last update: January 2007