Macrophage activation syndrome during treatment with biological therapy in patients with systemic juvenile idiopathic arthritis

Macrophage activation syndrome (MAS) is a severe complication of autoimmune diseases. It is more often associated with Systemic Juvenile Idiopathic Arthritis (sJIA). It is difficult to distinguish the MAS from a flare of sJIA, infection or medicinal side effects. The MAS can occur during a flare, an infection, a change in the medication or as a side effect of the treatment administered for the treatment of sJIA. Paradoxically have been reported MAS cases in patients with sJIA treated with anti IL-1 or anti IL-6R.