Macrophage activation syndrome: A fatal complication of systemic-onset juvenile idiopathic arthritis – A case report

Systemic-onset juvenile idiopathic arthritis (sJIA) is one of the most common pediatric chronic illnesses. The prevalence rate of the disease varies widely (3.5–5 cases/100,000). sJIA as a subtype includes about 10–15% of all juvenile idiopathic arthritis (JIA) [1]. sJIA is defined as arthritis affecting one or more joints usually in the juvenile age group (<16 years of age) with or preceded by fever of at least 2 weeks duration that is documented to be daily (“quotidian”) for at least 3 days which may be associated with evanescent erythematous rash (salmon pink) or generalized lymph node enlargement or hepatosplenomegaly and serositis, with a total duration of illness of >6 weeks. Macrophage activation syndrome (MAS) is a rare condition, reported to occur in the context of infectious, malignant, metabolic, and autoimmune diseases [2]. This potentially life-threatening complication has been found in approximately 7–13% of sJIA patients; although, subclinical MAS was found in bone marrow of more than 53% sJIA patients at the time of diagnosis [3]. However, diagnosis is often challenging as the disease can mimic infections and malignancies. We, hereby, report a case of a 6-year-old male patient who was diagnosed as sJIA with MAS. This case report highlights the association of MAS with sJIA and its clinical implications. Although this association is very rare, the pediatricians should be aware of the typical clinical presentation and laboratory investigations so as to timely diagnose and treat this complication.