Still Disease

Síndrome auto-inflamatório adquirido
 
Disease spectrum
  • Systemic-onset juvenile idiopathic arthritis: onset before 16 years old
  • Adult onset Still disease: onset at or after 16 years old
 
 
Juvenile Idiopathic Arthritis classified in 7 major types
  • Systemic-onset (Still disease)
  • Rheumatoid factor positive polyarticular
  • RF negative polyarticular
  • Oligoarticular
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Epidemiology
  • Juvenile Idiopathic Arthritis is the most common rheumatic disease in childhood
  • 0,2-1 per 1000 children
  • Systemic-onset represents 15-20% of all JIA
 
Mechanism: autoinflammatory disease (not autoimmune)
  • Activation of innate immune system
  • Dysregulated IL1 (hence response to IL1 antagonists)
    • IL1 → stimulates granulopoiesis in bone marrow
    • IL1 → activates thermoregulatory functions of the hypothalamus
  • IL-6 → stimulates osteoclastogenesis, production of C reactive protein
 
Clinical presentation
  • Skin → evanescent exanthem
    • Evanescent, erythematous eruption
    • Coincides with fevers
    • Transient, disappears within a few hours (<24h) without scar
    • Accompanied by arthralgias, but in 1/4 of patients rash may precede arthritis
    • Predilection for axillae and waist
    • May have persistent plaques, which may be linear
    • Periorbital erythematous edema
    • May have linear lesions due to Koebner
    • May have dermographism
  • Daily high fevers (usually >38,9ºC)
 
Complications
  • Macrophage activation syndrome
    • Fever, cytopenias, liver dysfunction, coagulopathy, hypofibrinogenimia, hypertriglyceridemia, high levels of ferritin
  • Severe interstitial lung disease due to alveolar proteinosis and/or endogenous lipoid pneumonia
    • Acute clubbing
 
Histology of evanescent exanthem
  • Perivascular and interstitial neutrophil-dominant mixed infiltrate ~neutrophilic urticarial dermatosis
 
DDx - “Still disease remains a diagnosis of exclusion after other causes, particularly infectious ones have been ruled out”
  • Leukemia, lymphoma
  • Parvovirus B19
  • Malaria
  • Chronic miningococcemia
  • Rat bite fever
  • Cystic fibrosis associated episodic arthritis
 
Treatment
  • NSAIDs
  • IL-1/IL-1R antagonists
    • Anakinra
    • Canakinumab
  • IL-6R antagonists
    • Tocilizumab
  • TNF inhibitors less effective
  • Conventional steroid sparing immunomodulators
    • MTX
    • Abatacept
    • Azathioprine
    • Leflunomide
  • Thalidomide
  • Hematopoietic stem cell transplantation