Macrophage activation syndrome in patients with systemic juvenile idiopathic arthritis treated with tocilizumab

Macrophage activation syndrome (MAS) is a severe, potentially fatal complication of systemic juvenile idiopathic arthritis (sJIA). Changes in therapies, including biologics, have been associated with the onset of MAS. Interleukin-6 (IL-6) plays a major pathogenic role in sJIA; data in animals suggest that high IL-6 levels contribute to the triggering of MAS [ 1 ]. Treatment with the IL-6 receptor inhibitor tocilizumab (TCZ) is highly effective in patients with sJIA [ 2 ].