Characterization of Patients with Macrophage Activation Syndrome Secondary to Systemic Juvenile Idiopathic Arthritis

The study aimed to analyze the clinical and laboratory characteristics of patients with systemic juvenile idiopathic arthritis (sJIA) who developed macrophage activation syndrome (MAS) and identify factors linked to MAS occurrence.

Patients with sJIA, diagnosed based on internationally recognized criteria, participated in the research. Retrospective clinical and laboratory data from inflammatory episodes complicated by MAS were evaluated. The Hemophagocytic Syndrome diagnostic score was calculated to assess its utility on pediatric population.

The study included 23 patients with systemic juvenile idiopathic arthritis (sJIA), of whom 7 (30%) experienced macrophage activation syndrome (MAS) during their disease course. At the time of admission, patients who developed MAS exhibited elevated liver enzymes: ALT (Median = 43, IQR: 25 - 473 vs. Median = 14, IQR: 12 - 30, p = 0.006) and AST (Median = 66, IQR: 51 - 666 vs. Median = 27, IQR: 25 - 33, p = 0.024). Similarly, during hospitalization, patients with MAS showed significantly higher AST levels (Median = 534, IQR: 111 - 1130 vs. Median = 31, IQR: 26 - 42, p = 0.020) and ALT levels (Median = 160, IQR: 46 - 559 vs. Median = 23, IQR: 14 - 48, p = 0.024). Additionally, they experienced a greater decrease in platelet count (Median = 119, IQR: 39 - 209 vs. Median = 306, IQR: 249 - 457, p = 0.004), higher white blood cell counts (Median = 29, IQR: 17 - 36 vs. Median = 18, IQR: 14 - 26, p = 0.021), and elevated D-dimer levels (Median = 16,800, IQR: 5,190 - 34,000 vs. Median = 1,851, IQR: 1,352 - 2,189, p = 0.006). No association was found between MAS and gender, muscle pain, hemophagocytosis in bone marrow aspirate, erythematous rash, or conjunctivitis. The Hemophagocytic Syndrome diagnostic score (HS score) at the optimal cutoff of 169 achieved a sensitivity of 86% and a specificity of 88%.

The findings underscore the significance of recognizing specific clinical and laboratory indicators, such as thrombocytopenia and elevated markers like D-dimers and liver enzymes, to identify sJIA patients at heightened risk for MAS. Prompt diagnosis and intervention are crucial to improving outcomes in this patient group. Key Points • The study identifies thrombocytopenia, elevated D-dimers, hypertriglyceridemia, and elevated liver enzymes (AST, ALT) as key laboratory predictors of macrophage activation syndrome (MAS) in systemic juvenile idiopathic arthritis (sJIA) patients. • Laboratory abnormalities, including high ferritin levels, thrombocytopenia, and impaired liver function, were highlighted as critical markers for distinguishing MAS from active sJIA. • Clinical factors such as erythematous rash and conjunctivitis were inversely associated with MAS occurrence, aiding differential diagnosis. • The findings emphasize the importance of early detection and routine monitoring of laboratory parameters to prevent delays in MAS diagnosis and improve patient outcome.