Successful salvage treatment with baricitinib for macrophage activation syndrome complicating adult-onset Still’s disease during interleukin-6 inhibition: A case report and literature review

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Adult-onset Still's disease (AOSD) is a systemic autoinflammatory disorder, and macrophage activation syndrome is a life-threatening hyperinflammatory complication. Interleukin-1 and interleukin-6 inhibitors have improved outcomes in refractory AOSD, but optimal management of macrophage activation syndrome, particularly when it develops during biologic therapy, remains uncertain. We report a case of a 49-year-old woman with articular-predominant AOSD who developed fulminant macrophage activation syndrome while receiving high-dose glucocorticoids, tacrolimus, and the interleukin-6 receptor inhibitor tocilizumab. At the onset of macrophage activation syndrome, she had persistent fever, cytopenia, hyperferritinemia, and liver dysfunction, and bone marrow examination revealed haemophagocytosis. Macrophage activation syndrome persisted despite two courses of intravenous methylprednisolone pulse therapy and continuation of tocilizumab. Tocilizumab was discontinued, and treatment was switched to the oral Janus kinase 1/2 inhibitor baricitinib in combination with glucocorticoids and tacrolimus. After this change, the patient experienced rapid defervescence, marked improvement in blood counts and ferritin levels, and sustained control of articular and systemic disease activity. Glucocorticoids were successfully tapered without relapse, and the patient remained in remission for more than 2 years without serious infections. To contextualise this case, we reviewed published reports on Janus kinase inhibition in AOSD, including cases complicated by macrophage activation syndrome. Multi-cytokine blockade through Janus kinase 1/2 inhibition, targeting overlapping interleukin-6, interferon-gamma, and granulocyte-macrophage colony-stimulating factor pathways, may simultaneously suppress macrophage activation and systemic inflammation. This case highlights the potential of baricitinib as a therapeutic option for refractory AOSD-associated macrophage activation syndrome during interleukin-6 inhibition.