Macrophage Activation Syndrome (MAS) is a rare but life threatening pro-inflammatory complication of multiple autoimmune diseases leading to cytokine storm. We report a case of MAS as a presenting manifestation of Systemic Lupus Erythematosus.

A 32-year-old female, newly diagnosed with Systemic Lupus Erythematosus (SLE), presents with a 3-month history of fever and joint pains, which began a few days after receiving her first dose of a viral vector COVID-19 vaccine. She later developed facial edema, and her fever became persistent and unremitting. Upon presentation, she was initially hypotensive, tachycardic, with distended neck veins, with periorbital edema and muffled heart sounds. Initial work-up revealed pericardial effusion, anemia, thrombocytopenia, elevated creatinine, hypoalbuminemia, hematuria, and pyuria. She was intubated, started on inotrope, and underwent pericardiocentesis. Patient was classified as SLE based on Systemic Lupus International Collaborating Clinics Classification (SLICC) Criteria despite negative antinuclear antibody (ANA). Nevertheless, she was started on IV steroids and hydroxychloroquine. She was eventually extubated after significant clinical improvement. Further work-up for MAS was however done due to persistent febrile episodes. Hyperferritinemia, hypertriglyceridemia, hypercholesterolemia, pancytopenia, transaminitis, and splenomegaly on imaging were noted. She was then started on methylprednisolone pulse therapy. After treatment, marked clinical improvement, as well as resolution of transaminitis and pancytopenia were noted.

A high index of suspicion for MAS should exist in a patient with pyrexia of unknown origin with concomitant autoimmune disease. In this disease that can lead to progressive organ failure, early diagnosis and management is crucial. This case report culminates the need for diagnostic and therapeutic guidelines that will help in the early diagnosis and immediate treatment of this debilitating condition.