This protocol applies to patients under 18 years of age with systemic juvenile idiopathic arthritis (sJIA) complicated by macrophage activation syndrome (MAS), in whom a course of IL-1 and IL-6 inhibitor therapy has not achieved the defined treatment goals.
Macrophage activation syndrome is a serious complication of systemic JIA. Up to 40% of cases of systemic JIA are associated with MAS — a secondary hemophagocytic syndrome that is a life-threatening complication requiring urgent recognition and treatment. It presents with a characteristic set of findings:
The prior treatment step involved alternative IL-1 or IL-6 inhibitors — anakinra, canakinumab, or tocilizumab — with switching among and between these agents as needed. The goals of that line were inactive disease and resolution of macrophage activation syndrome. When those targets are not achieved, the next treatment step is indicated.
For joint disease that persists after IL-1 and IL-6 inhibitor therapy, disease-modifying therapy is the recommended direction — biologic DMARDs or csDMARDs are strongly recommended over long-term glucocorticoids. The specific agent selection, switching sequence, and full regimen are available in the complete protocol.
Clinical goals: resolution of residual joint synovitis · inactive disease
Up to 40% of cases of systemic JIA are associated with MAS, a secondary hemophagocytic syndrome that is a life-threatening complication requiring urgent recognition and treatment.
MAS presents with fevers, high ferritin levels, cytopenias, elevated liver enzyme levels, low fibrinogen levels, and high triglyceride levels.
Biologic DMARDS or csDMARDs are strongly recommended over long-term glucocorticoids for residual arthritis and incomplete response to IL-1 and/or IL-6 inhibitors.
There are many options (e.g., adding methotrexate, switching to abatacept or a TNFi), and ample evidence supports the use of DMARDs for systemic JIA–associated synovitis.
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