Systemic onset juvenile idiopathic arthritis

Systemic-onset JIA (S-JIA) comprises around 10% of JIA (1,2)

• it is responsible for a significant percentage of the morbidity and mortality caused by JIA
• affects both female and males with the same frequency
• may occur at any time during childhood
• unlike patients with other categories of JIA, those with systemic JIA present with markedly elevated levels of inflammatory markers, fevers, and rashes (3)
  • in the initial presentation, arthritis may not be present
• early in the disease course, systemic JIA resembles monogenic autoinflammatory syndromes such as familial Mediterranean fever

Presentation of the condition (1,2)

• arthritis
  • normally polyarticular
  • presents within the first 3 months of onset
• extra-articular features
  • intermittent fever for at least 2 weeks plus one of the following
    • temperature rises up to 39.5 °C once or twice in a day
    • generally accompanied by a typical, salmon pink-coloured rash
  • typical rash
    • classic salmon-coloured evanescent rash
    • there is discrete circumscribed macules that may be surrounded by a ring of pallor or develop central clearing
    • vanishes with the decline of the fever
    • found most commonly on the trunk, axilla, and inguinal areas
    • may be exacerbated by stress, or a hot bath
  • generalized lymphadenopathy
    • seen in about one-third of patients
  • hepatosplenomegaly
    • seen in about one-third of patients
  • serositis
    • includes pericarditis and pleuritis

Note:

• fever and rash generally resolve after the emergence of polyarthritis making the diagnosis of S-JIA difficult to differentiate from regular polyarticular JIA

Reference:

1. Barut K, Adrovic A, Şahin S, Kasapçopur Ö. Juvenile Idiopathic Arthritis. Balkan Medical Journal. 2017;34(2):90-101.
2. Kahn P.Juvenile idiopathic arthritis - an update on pharmacotherapy. Bull NYU Hosp Jt Dis. 2011;69(3):264-76.
3. Sandborg CI et al. Juvenile Idiopathic Arthritis. NEJM 2025;393:162-174