pediatrics
Juvenile Idiopathic Arthritis (JIA)
Macrophage Activation Syndrome
Macrophage activation syndrome is Hemophagocytic Lymphohistiocytosis (HLH) associated with Macrophage activation syndrome is a severe, overwhelming, and life-threatening cytokine storm syndrome caused by an uncontrolled macrophage and T lymphocyte expansion. It occurs in 10% of children with systemic JIA. Features of macrophage activation syndrome include high, nonremitting fever, hepatosplenomegaly, generalized lymphadenopathy, rash, hemorrhagic manifestations, central nervous system dysfunction (including seizures and coma), and shock. Features that help distinguish macrophage activation syndrome from systemic JIA include the constant fever (unlike the intermittent daily fevers of JIA), constant rash (unlike the transient rash of systemic JIA), hemorrhagic manifestations, seizures, coma, and shock. Despite marked systemic inflammation, the erythrocyte sedimentation rate (ESR) is paradoxically depressed because of low fibrinogen levels. Often, however, macrophage activation syndrome cannot be differentiated from active systemic JIA; discriminatory criteria have been developed and include ferritin > 684 ng/mL ( > 684 mcg/L)plusany 2 of the following: Platelets ≤ 181,000/mcL (≤ 181 × 109/L) Aspartate aminotransferase > 48 units/L (> 0.80 microkat/L) Triglycerides > 156 mg/dL (> 1.76 mmol/L) Fibrinogen ≤ 360 mg/dL (≤ 10.58 g/L) Macrophage activation syndrome has a mortality rate of 8% because of multiorgan failure. No consensus exists regarding specific treatment. Macrophage activation syndrome may respond well to successful treatment of the underlying rheumatic disease. Specific treatment of this syndrome in systemic JIA usually includes high-dose corticosteroids and may include other drugs (eg,cyclosporine, interleukin [IL]-1 inhibitors,cyclophosphamide) and stem cell transplantation. 