Sudden death due to neuroleptic malignant syndrome (NMS), which is caused by the use of psychoneurotic agents, is considered difficult to diagnose solely on the basis of autopsy examinations commonly conducted to identify the cause of death. In this study, we focused on ubiquitin (Ub); a stress protein, and ryanodine receptor (RyR); a Ca
2+ release channel protein, and investigated whether these proteins can serve as indicators useful for forensic diagnosis of death from NMS. Organs from 12 cases of NMS and 15 non-NMS cases were subjected to immunohistochemical staining with anti-Ub and anti-RyR antibodies, and expression of the two proteins were observed and compared. The percentage of Ub-positive cells was found to be high in skeletal muscle from NMS cases. However, in the case of non-NMS in psychiatric and neurological agents used, sometimes a high percentage of Ub-positive cell number in skeletal muscle, it is not a diagnostic indicator of the NMS. On the other hand, the percentage of RyR-positive cells was found to be high in psoas major and hypothalamus from NMS cases. That is, when the RyR-positive cells in the psoas muscle and hypothalamus were observed more than onethird of the observation field of view, may be able to diagnose the NMS, was considered to be one of the useful indicator for forensic diagnostics.
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