Children and adolescents
Systemic JIA / macrophage activation syndrome
Daily spiking fevers with rash and arthritis. Cytopenias and a rising ferritin signal MAS, a life-threatening emergency.
What to look for
- Quotidian fever for 2 weeks or more, evanescent rash, arthritis, serositis, hepatosplenomegaly
- MAS signs: persistent fever with a falling platelet count, very high or rising ferritin, raised AST, triglycerides and LDH, low fibrinogen, coagulopathy
- 2016 classification in sJIA: ferritin above 684 ng/mL plus 2 of platelets ≤181,000, AST above 48 U/L, triglycerides above 156 mg/dL, fibrinogen ≤360 mg/dL
What to do
- Suspected MAS needs the emergency department and same-day pediatric rheumatology. ICU care is often needed.
- Exclude infection and malignancy (leukemia, neuroblastoma) before diagnosing sJIA.
- The 2026 ACR guideline recommends IL-1 or IL-6 inhibitors as first-line therapy for sJIA. With MAS, a biologic plus systemic glucocorticoids is recommended.
About this urgency level
Call rheumatology directly. Many of these need the emergency department or admission, and treatment often starts before the specialist visit.
Timeframes are typical targets. Local pathways, capacity and clinical judgment come first.