Post-mortem methemoglobinemia: A retrospective analysis of forensic autopsy cases with elevated methemoglobin levels

Methemoglobinemia is rarely reported beyond isolated case reports in forensic literature, and comparative analyses of cases with elevated postmortem methemoglobin (MetHb) levels are rare. This study aims to identify such cases and assess links between elevated MetHb and the cause of death.

Crime scene, autopsy, and toxicology reports of cases autopsied at the Morgue Department of the Council of Forensic Medicine in Istanbul, between 2022 and 2024, were retrospectively reviewed. The study included cases in which elevated blood MetHb levels were detected post-mortem.

A total of 95 cases showed elevated blood MetHb levels after autopsy. Of these, 26 were women (27.4%), and 69 were men (72.6%), with an average age of 42.5 ± 20.4 years. The most common cause of death (n = 41) was smoke or gas inhalation or burns. The highest blood MetHb level was observed in deaths from smoke/gas asphyxiation (burns), at 32.4%. In 74.7% of cases, drugs/chemicals identified as causing MetHb in previous articles were detected in this study. Additionally, drugs and chemicals previously not associated with MetHb were detected in this study. The highest MetHb levels were observed in groups with COHb levels of 0%, 0.1%, and 10%. As the COHb group level increased, the average MetHb level decreased (p = 0.021).

The current study identified a range of drugs present in the blood of cases with elevated MetHb levels, expanding upon those previously reported. Furthermore, unlike some previous studies, a negative correlation was observed between MetHb and COHb levels. These results highlight the need for more comprehensive clinical, autopsy, and laboratory investigations to determine the contribution of various drugs to increased MetHb levels and to further elucidate the relationship between MetHb and COHb levels.