Abstract: Objective To investigate Fas protein expression of the myocardium in dilated cardiomyopathy （DCM） and its relationship with occurrence of sudden death caused by DCM. Methods Nine autopsy cases of sudden death caused by DCM along with the heart samples were chosen from the archives in the Department of Forensic Medicine, Tongji Medical College, HUST from 1997 to 2007. Other 11 cases which died of violence and other diseases were selected as the control group. Expressions of myocardial Fas protein in the samples were quantitatively detected by immunohistochemistry and computerized imaging analysis. Results Myocardial Fas protein expression increased significantly in the DCM group. Positive color showed brown-yellow granulated or striped distribution in the longitudinal section of myocardial within the cell membrane and cytoplasm, and showed circular brown granules in the cross section of the cell membrane, while these changes were not observed in the control group though there was focal weak staining noted. Statistical significance was observed between the experimental and control groups（P=0.002）, but no statistical significance was found for the average optical density value between these two groups（P=0.675）. Conclusion The expression of Fas protein increased obviously in the DCM group. Such alteration in expression quantity and distribution of myocardial Fas protein may be related to arrhythmia and heart failure in the patients with DCM.

Key words: forensic pathology, cardiomyopathy, dilated, immunohistochemistry, Fas protein