Primary varicella infection in children with systemic juvenile idiopathic arthritis under tocilizumab therapy

Area of Science:

• Immunology
• Pediatrics
• Rheumatology

Background:

• Systemic juvenile idiopathic arthritis (sJIA) is a chronic inflammatory condition in children.
• Tocilizumab is a biologic therapy targeting interleukin-6 (IL-6) for sJIA treatment.
• Varicella (chickenpox) is a common viral infection with potential complications in immunocompromised individuals.

Observation:

• Six children with sJIA on tocilizumab therapy contracted primary varicella infection.
• Clinical courses were monitored, including viral symptoms and sJIA disease activity.
• Serum cytokine levels, specifically IL-6 and IL-18, were measured during infection.

Findings:

• No disseminated or fatal varicella infections occurred in the observed cohort.
• One patient developed macrophage activation syndrome (MAS), a serious complication.
• Another patient experienced a relapse of their sJIA arthritis.
• All patients showed elevated serum IL-6 levels.
• Elevated serum IL-18 levels were noted in patients who developed MAS or arthritis relapse.

Implications:

• Tocilizumab may mitigate severe varicella complications in sJIA patients.
• Elevated IL-6 and IL-18 levels during varicella could indicate a risk for sJIA flare-ups.
• Monitoring IL-18 may be beneficial in sJIA patients with varicella infection.
• Further research is needed to understand the interplay between varicella, tocilizumab, and sJIA pathogenesis.