Abstract: Objective To explore the distribution of inflammatory cells and positive expression of P-selectin glycoprotein ligand-1 （PSGL-1） in infant brainstem tissue from hand-foot-mouth disease related fatal brainstem encephalitis. Methods Twenty brainstem samples from infants suffered from brainstem encephalitis were collected as the experimental group. Ten brainstem samples from infants died of non-brain diseases and injuries were collected as the control group. The distribution of inflammatory cells and the expression of PSGL-1 in the two groups were examined by immunohistochemical method. The characteristics of the positive cells were observed. Results In brainstem tissue of the experimental group, there were sleeve infiltrations of inflammatory cells around the vessels and in the glial nodule. Microglia was the most and following was neutrophils around the vessels and in the glial nodule. There was a significant statistical difference among microglias, neutrophils and lymphocytes （P<0.05）. There was no sleeve infiltration in the control group. PSGL-1 protein was expressed widely in inflammatory cells in the experimental group, especially in the inflammatory cells around the vessels and in the glial nodule. But PSGL-1 positive staining could be observed significantly less in the control group comparing with the experimental group （P<0.05）. Conclusion Microglia is the main type of inflammatory cells involved in the progress of the fatal disease. Moreover, PSGL-1 could participate in the pathogenesis of hand-foot-mouth disease related fatal brainstem encephalitis.

Key words: forensic pathology, hand, foot and mouth disease, brain stem encephalitis, inflammatory cell, P-selectin glycoprotein ligand-1, infant