Successful treatment of macrophage activation syndrome complicating adult Still disease with anakinra

A previously healthy 20-year-old man presented with adult Still disease (ASD). He developed life-threatening macrophage activation syndrome (MAS), which was refractory to standard immunosuppression but responded dramatically to the IL-1 receptor antagonist anakinra. Subsequent immunological investigations included assessment of the perforin expression of natural killer (NK) cells and CD8+ T cells, which confirmed MAS.