Ravelli et al reported criteria for the diagnosis of the macrophage activation syndrome (MAS) in patients with systemic juvenile idiopathic arthritis (JIA). The authors are from the Paediatric Rheumatology International Trials Organisation, the Childhood Arthritis and Rheumatology Research Alliance, the Pediatric Rheumatology Collaborative Study Group, the Histiocyte Society, European League Against Rheumatism (EULAR), and the American College of Rheumatology (ACR).
Criteria the diagnosis of MAS in systemic JIA:
(1) fever
(2) known or suspected systemic JIA
(3) serum ferritin > 684 ng/mL
(4) 2 or more of the following
(4a) platelet count <= 181,000 per µL
(4b) serum AST > 48 U/L
(4c) serum triglycerides > 156 mg/dL
(4d) plasma fibrinogen <= 360 mg/dL
(5) exclusion of alternative causes for laboratory findings (ITP, hemochromatosis, infectious hepatitis, etc)
where:
• The method and upper limit of normal (ULN) for serum AST not formally stated. The highest value for a patient without MAS was 45, so it is presumed that it represents greater than ULN. Alternatively it may be set at 1.5 times the ULN.
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