A Cytokine Storm Unveiled: Diagnostic Challenges of Macrophage Activation Syndrome in the Context of Undiagnosed Systemic Lupus Erythematosus in an Adolescent.

Macrophage activation syndrome (MAS) is part of a spectrum of cytokine storms. This case report describes a presentation of an 18-year-old female with systemic lupus erythematosus (SLE) complicated by MAS. The patient, previously healthy, presented with a 3-week history of high-grade intermittent fever, abdominal pain, nausea, and loss of appetite. Clinical examination revealed fever, tachycardia, and normal blood pressure without signs of lymphadenopathy or organomegaly. Laboratory tests indicated anemia, thrombocytopenia, leukopenia, neutropenia, elevated liver enzymes, hyperferritinemia, hypofibrinogenemia, and hypertriglyceridemia. Despite broad-spectrum antimicrobial therapy, the patient's fever persisted, prompting bone marrow aspiration, which showed hemophagocytosis. Immunological testing revealed elevated antinuclear antibodies, anti-double-stranded DNA, and anti-Smith antibodies, confirming a diagnosis of SLE. Further analysis using the Modified Histocyte score and hemophagocytic lymphohistiocytosis-2004 criteria supported a diagnosis of MAS associated with SLE. The patient was treated with intravenous methylprednisolone, followed by oral prednisolone and monthly cyclophosphamide. The patient showed significant clinical improvement with the resolution of fever and hematological abnormalities. MAS is a rare but severe complication of SLE, requiring early recognition and treatment to prevent life-threatening complications like multiorgan failure. This case highlights the importance of considering MAS in young females with SLE presenting with systemic symptoms and emphasizes using diagnostic scoring systems to guide management. Early intervention and careful monitoring are crucial to improving patient outcomes.