Secondary hemophagocytic lymphohistiocytosis (hemophagocytic syndrome, massive macrophage activation syndrome) is a rare, aggressive, severe syndrome with a frequent fatal outcome. The pathogenesis of the syndrome, the role of viral infection, and the development of an excessive, aberrant, and inflammatory response leading to multiple organ dysfunction and sepsis remain unclear so far. The paper presents the data available in the literature and describes the authors’ own observation of secondary hemophagocytic lymphohistiocytosis in a 14-year-old girl who had Epstein—Barr virus infection and died of severe multiple organ dysfunction. The in vivo diagnosis was based on the typical clinical presentations of the disease, the detection of the virus by a polymerase chain reaction assay, and the determination of blood ferritin levels. Contemporary morphological diagnostic criteria (immunohistochemical reactions with anti-EBV and anti-CD68 monoclonal antibodies; Epstein—Barr virus encoded RNA (EBER) in situ hybridization) are shown; and clinical and pathological comparisons have been made.