Macrophage activation syndrome: advances towards understanding pathogenesis

Area of Science:

• Immunology
• Pediatric Rheumatology
• Hematology

Background:

• Macrophage activation syndrome (MAS) is a severe complication in pediatric rheumatology, particularly systemic juvenile idiopathic arthritis (SJIA).
• Current diagnostic criteria for MAS are lacking, hindering early detection and treatment.
• MAS shares similarities with familial hemophagocytic lymphohistiocytosis (FHLH), suggesting underlying genetic and pathway defects.

Purpose of the Study:

• To review advancements in understanding MAS pathophysiology.
• To identify potential diagnostic biomarkers for early MAS detection in SJIA.

Main Methods:

• Literature review focusing on MAS pathophysiology, genetic defects, and macrophage characteristics.
• Analysis of recent gene expression studies and phenotypic characterization of hemophagocytic macrophages.

Main Results:

• Cytolytic function is significantly impaired in SJIA patients with MAS.
• Hemophagocytic macrophages expressing CD163 are expanded in a subset of SJIA patients, potentially indicating early MAS.
• These macrophages are involved in adapting to oxidative stress from free iron.

Conclusions:

• Advances in understanding hemophagocytic macrophage expansion offer potential new biomarkers for MAS.
• These biomarkers could improve clinical diagnosis and management of MAS in SJIA.