P153 Interleukin-6 levels as indicator of macrophage activation syndrome/relaps in systemic juvenile arthritis during anakinra or tocilizumab treatment

Abstract

Introduction Systemic juvenile idiopathic arthritis (sJIA) without arthritis is a subtype of chronic childhood arthritis of presumed autoinflammatory etiology. It is characterized by prolonged period of spiking fever, skin rash, lymphadenopathy, hepatosplenomegaly, and serositis. Macrophage activation syndrome (MAS), a potentially fatal complication is seen most frequently in this juvenile rheumatic disease. MAS is diagnosed based on the combination of clinical symptoms, cytopenia or sudden decrease of white blood cells and/or platelet count, coagulopathy, and liver dysfunction in the absence of infection. Ample evidence supports the hypothesis that MAS is one of many presentations of cytokine storm scenarios in human diseases. Some of these cytokines are target molecules of biologic therapy in sJIA such as interleukin (IL)-1 and IL-6. In addition to anakinra, recombinant IL-1RA, a tocilizumab (TCZ), a humanized anti-IL-6 receptor monoclonal antibody, is approved for treatment of sJIA also. Methods Here we present a comparison of laboratory findings of two separate acute non-infectious exacerbations in a 6 years old girl with multiple-drug resistant sJIA that developed during treatment with anakinra or TCZ. Results Although both treatments resulted in rapid resolution of systemic symptoms initially, anakinra treatment was superior in the length of disease remission. Treatment with anakinra did not interfere with findings of laboratory evaluation recommended for diagnosis of the acute phase of sJIA and/or MAS. In contrast to anakinra, TCZ blocked the production of C-reactive protein while other soluble markers such as serum IL-6, procalcitonin, and ferritin were unaffected. Conclusion These findings indicate that laboratory monitoring of exacerbations in sJIA patients should be tailored based on the type of the blockade of a single cytokine pathway (IL-1 or IL-6).