Macrophage activation syndrome

Macrophage Activation Syndrome (MAS) is a severe, potentially life-threatening complication of systemic juvenile idiopathic arthritis (sJIA) and other autoimmune diseases. It is characterized by excessive activation and proliferation of macrophages and T lymphocytes, leading to overwhelming inflammation and tissue damage.

Pathophysiology

MAS is a form of secondary hemophagocytic lymphohistiocytosis (HLH), a syndrome of excessive immune activation. In MAS, the dysregulated immune response leads to the overproduction of cytokines, such as interleukin-1, interleukin-6, and tumor necrosis factor-alpha. This cytokine storm results in the activation of macrophages and T cells, which then attack the body's own tissues.

Clinical Features

The clinical presentation of MAS includes:

• Persistent high fever
• Hepatosplenomegaly (enlarged liver and spleen)
• Cytopenias (reduction in the number of blood cells)
• Elevated levels of ferritin
• Hypertriglyceridemia (high levels of triglycerides in the blood)
• Coagulopathy (impaired blood clotting)

Diagnosis

The diagnosis of MAS is challenging due to its overlap with other inflammatory conditions. It is often based on clinical criteria and laboratory findings, including:

• Elevated serum ferritin levels
• Decreased platelet count
• Elevated liver enzymes
• Hypertriglyceridemia
• Hypofibrinogenemia (low levels of fibrinogen)

Treatment

Early recognition and treatment of MAS are crucial. Treatment typically involves:

• High-dose corticosteroids
• Cyclosporine
• Intravenous immunoglobulin (IVIG)
• Biologic agents targeting specific cytokines, such as anakinra (an interleukin-1 receptor antagonist)

Prognosis

The prognosis of MAS depends on the promptness of diagnosis and initiation of treatment. With timely and appropriate therapy, the outcome can be favorable, but delayed treatment can lead to significant morbidity and mortality.

Related Pages

• Systemic juvenile idiopathic arthritis
• Hemophagocytic lymphohistiocytosis
• Cytokine storm
• Autoimmune diseases
• Macrophage
• T lymphocytes