macrophage activation syndrome
Also written as: MAS — macrophage activation syndrome
A life-threatening complication of systemic JIA characterized by excessive immune activation and cytokine storm.
Full Definition
Macrophage activation syndrome (MAS) is a severe, potentially fatal complication most commonly associated with systemic onset juvenile idiopathic arthritis. It represents a form of secondary hemophagocytic lymphohistiocytosis characterized by uncontrolled activation of macrophages and T-lymphocytes, leading to excessive cytokine production and consumption of blood cells. Clinical features include persistent high fever, hepatosplenomegaly, coagulopathy, and neurological symptoms. Laboratory findings show falling blood counts, elevated ferritin levels, and evidence of liver dysfunction. Prompt recognition and aggressive treatment with immunosuppressive therapy are essential for survival.
Usage
Usage note: Always specify as complication of underlying rheumatic condition when documenting diagnosis.
In Context
- "The patient developed macrophage activation syndrome requiring immediate high-dose corticosteroid therapy." — Emergency department note
- "Falling platelet counts and rising ferritin levels raised concern for macrophage activation syndrome." — Laboratory interpretation