Abstract
INTRODUCTION AND IMPORTANCE: Macrophage activation syndrome (MAS) is a severe form of hemophagocytic lymphohistiocytosis that is frequently associated with either a flare-up of rheumatologic diseases, or infection and is characterized by intermittent fever, organomegaly, and multisystem dysfunction. Early diagnosis and treatment are crucial for outcome improvement. CASE PRESENTATION: The authors present a 9-year-old male with systemic onset juvenile idiopathic arthritis who presented with fever, vomiting, and nose bleeding, as well as being jaundiced, and having hepatomegaly and ascites. Pancytopenia, hepatic dysfunction, and elevated ferritin levels were discovered, along with negative virological and immunological tests. He was given broad-spectrum antibiotics, and a high-dose steroid showed a good response, and he was discharged about a week later. CLINICAL DISCUSSION: It is hypothesized that decreased natural killer cells' function could lead to the inability to clear the infection, and subsequent lymphocytes-induced macrophages activation. Despite being beneficial in this case, steroids led to no improvement in other similar cases. CONCLUSION: MAS is a real life-threatening complication for patients with systemic Juvenile idiopathic arthritis (sJIA), and early diagnosis and prompt initial treatment can both offer a favourable result against such syndrome.