Introduction: Macrophage activation syndrome (MAS) is a severe complication of systemic juvenile idiopathic arthritis (sJIA).
Objective: To describe the clinical characteristics and outcome of patients diagnosed with MAS in Spanish pediatric rheumatology units.
Patients and method: A protocol for data collection was designed and distributed to pediatricians and rheumatologists attending children with rheumatic diseases.
Results: Information was available from 31 patients (16 boys and 15 girls) who had 37 MAS episodes. Twenty-seven children had only one episode, three had two episodes and one had four episodes. The interval between episodes ranged from 1 to 33 months. The median age was 5.9 years (range 1-23). MAS was the initial manifestation of sJIA in nine patients. The most frequent symptom was fever (97%), followed by skin rash (49%), central nervous system dysfunction (41%), and gastrointestinal abnormalities (15%). Abnormal laboratory findings included thrombopenia (78%) and elevated levels of hepatic enzymes (70%). Hemophagocytosis was confirmed in 16 of 30 bone marrow samples evaluated, 15 with cyclosporine A and six with etoposide. All episodes but one were treated with steroids. One patient received a liver transplant before diagnosis. The mortality rate was 6.5% (2/31).
Conclusion: MAS is a severe, potentially lethal, complication of sJIA. The clinical and laboratory abnormalities characteristic of sJIA complicate its diagnosis. The earliest and most frequent findings were decreased in platelet count and elevation of hepatic enzymes. A high degree of suspicion as well as early diagnosis and prompt treatment are essential in this disease.