Fatal unexpected death due to familial hemophagocytic lymphohistiocytosis type 3.

Familial hemophagocytic lymphohistiocytosis is a rare autosomal recessive disorder of immune dysregulation associated with uncontrolled activation of cytotoxic T cells and macrophages. Herein, we report a case of a 14-month-old Chinese boy who presented with fever, abdominal distension and thrombopenia, and died within 3 days of admission to the hospital. Postmortem examination revealed pleuroperitoneal fluid, enlarged mesenteric lymph nodes and hepatosplenomegaly. Histopathological examination showed interstitial pneumonia, hepatonecrosis and hemophagocytosis. Immunohistochemical staining of the spleen, lymph node and liver specimens revealed numerous cytotoxic T cells (CD8+) and histiocytes (CD68+). EBER1-positive cells were observed in lymphocytes of the spleen, lymph node, liver and lungs by in situ hybridization. UNC13D mutation was identified, although the boy had no family history. The following medico-legal autopsy case is being reported for its rarity in the forensic setting. We addresses the need for genetic testing in addition to a thorough clinical history, appropriate laboratory tests, histological examination and immunohistochemical analysis for the rapid and accurate diagnosis of familial hemophagocytic lymphohistiocytosis.