Macrophage Activation Syndrome Associated with Adult-Onset Still's Disease Successfully Treated with Anakinra.

Macrophage activation syndrome (MAS) is a potentially fatal complication of Adult-Onset Still's disease (Still's disease). Whereas an increasing body of evidence supports interleukin-1 (IL-1) blockade as a promising treatment for Still's disease, whether it is therapeutic for MAS associated with Still's disease remains unclear. We report a 34-year-old Caucasian man with one-decade history of TNF-blockade-responsive seronegative arthritis who presented with abrupt onset of fever, serositis, bicytopenia, splenomegaly, hepatitis, and disseminated intravascular coagulation. Striking hyperferritinemia was noted without evidence of infection, malignancy, or hemophagocytosis on bone marrow biopsy. NK cells were undetectable in the peripheral blood, whereas soluble IL-2 receptor was elevated. His multiorgan disease resolved in association with methylprednisolone pulse therapy, Anakinra, and a tapering course of prednisone. This case reinforces the notion that Still's disease is inherently poised to manifest MAS as one of the clinical phenotypes by shedding light on the role of IL-1 underlying both Still's disease and related MAS.