Abstract
A 768 g female neonate, born at 25 weeks' gestation, developed sepsis due to methicillin-resistant Staphylococcus epidermidis on day 14. Severe thrombocytopenia was observed, and hemophagocytic macrophages were identified in her peripheral blood smear. Cytokine profiles at the time of onset suggested that an inflammatory cytokine storm had activated lymphocytes and macrophages, leading to platelet phagocytosis. After administration of vancomycin for 14 days and immunoglobulin therapy, she improved without any complications. Considering the results of cytokine profiles, early intervention for infection may have prevented progression to hemophagocytic lymphohistiocytosis and reduced the severity of clinical symptoms.