New Criteria Released for Macrophage Activation Syndrome in Juvenile Idiopathic Arthritis

“The use of cut-off valves are not as useful as observing closely the trend of laboratory results, especially since it’s imperative to make an early diagnosis of MAS,” he says. Another paper co-authored by Drs. Ravelli and Cron, as well as Dr. Schneider, in the EULAR journal Rheumatic & Musculoskeletal Diseases, also stresses the importance of laboratory values changes over time in making a diagnosis of MAS in systemic JIA patients.²

Another caveat to note is that many systemic JIA patients are now treated with either the IL-1 inhibitor canakinumab or the IL-6 inhibitor tocilizumab. These drugs inhibit two of the pro-inflammatory cytokines that the immune system oversecretes during MAS. So patients treated with one of these two drugs may not present with either high fever or the typical laboratory features of MAS, such as a peak ferritin level of 684 ng/mL. Or their presenting features may be milder, not meeting the criteria.

“Although these agents have proven efficacy in treating systemic JIA, it is clear that their use does not prevent MAS from occurring in these patients,” says Dr. Schneider.

The significant morbidity and mortality associated with systemic JIA patients who develop MAS makes the need for more accurate clinical trial recruitment and therapeutic development urgent and important.

“This makes the case not only for the need for early diagnosis and treatment, but also for more effective treatments that are better tolerated than some of the currently available treatment options,” says Dr. Schneider. “Widely accepted classification criteria will almost certainly be helpful in facilitating the prospective study of MAS in systemic JIA, and hopefully will facilitate the identification of new biomarkers and new, targeted therapies.”

Susan Bernstein is a freelance medical journalist based in Atlanta.

References

1. Ravelli A, Minoia F, Davi S, et al. 2016 Classification Criteria for Macrophage Activation Syndrome Complicating Systemic Juvenile Idiopathic Arthritis: A European League Against Rheumatism/American College of Rheumatology/Paediatric Rheumatology International Trials Organisation Collaborative Initiative. Arthritis Rheum. 2016 March;68(3):566–576. doi:10.1002/art.39332.
2. Ravelli A, Minoia F, Davi S, et al. Expert consensus of dynamics in laboratory tests for diagnosis of macrophage activation syndrome complicating systemic juvenile idiopathic arthritis. RMD Open. 2016 Jan 19;2(1):e000161.