Which clinical history findings are characteristic of macrophage activation syndrome (MAS)?

Updated: Nov 21, 2018
  • Author: Angelo Ravelli, MD; Chief Editor: Lawrence K Jung, MD  more...
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The clinical presentation of macrophage activation syndrome (MAS) is generally acute and occasionally dramatic. Typically, patients become acutely ill with the sudden onset of nonremitting high fever, profound depression in all 3 blood cell lines (ie, leukopenia, anemia, and thrombocytopenia), hepatosplenomegaly, lymphadenopathy, and elevated serum liver enzyme levels. High levels of triglycerides and lactic dehydrogenase and low sodium levels are consistently observed.

The coagulation profile is often abnormal, with prolongation of prothrombin time (PT) and partial thromboplastin time (aPTT), hypofibrinogenemia, and detectable fibrin degradation products. In children with systemic juvenile idiopathic arthritis, the clinical picture may mimic sepsis or an exacerbation of the underlying disease. However, the pattern of nonremitting fever is different from the remitting high-spiking fever seen in systemic juvenile idiopathic arthritis. Moreover, patients may show a paradoxical improvement in the underlying inflammatory disease at the onset of macrophage activation syndrome, with disappearance of signs and symptoms of arthritis and a precipitous fall in the erythrocyte sedimentation rate. The latter phenomenon probably reflects the degree of hypofibrinogenemia secondary to fibrinogen consumption and liver dysfunction. [20]

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