Macrophage activation syndrome (MAS) is a fatal complication in rheumatic diseases. It is characterized by prolonged fever, pancytopenia, and hepatosplenomegaly, which are consequences of uncontrolled macrophage activation. MAS in children is most commonly associated with systemic juvenile idiopathic arthritis. Its association with systemic lupus erythematosus (SLE) is relatively rare, so we report a Thai boy who initially presented with MAS and eventually was diagnosed as having SLE. He also had recurrent MAS during the course of therapy. Hyperferritinemia is one of the abnormal laboratory findings in MAS and it has been used as an inflammatory marker. However, its correlation with disease activity remains unclear. Therefore, a review of literature regarding MAS-associated SLE in children and ferritin level in this disease was carried out.