Objective To explore the distribution of inflam m atory cells and positive expression of P-se-lectin glycoprotein ligand-1 (PSG L-1) in infant brainstem tissue from hand-foot-m outh disease related fatal brainstem encephalitis. Methods Tw enty brainstem sam ples from infants suffered from brainstem en-cephalitis w ere collected as the experim ental group. Ten brainstem sam ples from infants died of non-brain diseases and injuries w ere collected as the control group. The distribution of inflam m atory cells and the expression of PSG L-1 in the tw o groups w ere exam ined by im m unohistochem ical m ethod. The characteristics of the positive cells w ere observed. Results In brainstem tissue of the experim ental group, there w ere sleeve infiltrations of inflam m atory cells around the vessels and in the glial nodule. Microglia was the m ost and following was neutrophils around the vessels and in the glial nodule. There was a significant statistical difference am ong m icroglias, neutrophils and lym phocytes (P<0.05). There was no sleeve infiltration in the control group. PSG L-1 protein was expressed w idely in inflam m atory cells in the experim ental group, especially in the inflam m atory cells around the vessels and in the glial nodule. B ut PSG L-1 positive staining could be observed significantly less in the control group com paring with the experim ental group (P<0.05). Conclusion Microglia is the m ain type of inflam m atory cells involved in the progress of the fatal disease. Moreover, PSG L-1 could participate in the pathogenesis of hand-foot-m outh disease related fatal brainstem encephalitis.