In a case of suspected poisoning, the pathologist notices a cherry-red discolouration of the postmortem hypostasis. The MOST likely toxin responsible is:
- A Organophosphorus compound
- B Potassium cyanide ✓
- C Arsenic trioxide
- D Ethanol
Explanation
Cherry-red lividity (postmortem hypostasis) is classically seen in carbon monoxide and cyanide poisoning. Both produce carboxyhaemoglobin (CO) and cyanmethaemoglobin respectively, which maintain haemoglobin in a stable oxygenated-looking configuration. Cyanide inhibits cytochrome c oxidase, preventing oxygen utilisation so that haemoglobin remains oxygenated. Organophosphorus poisoning causes no distinctive lividity colour; arsenic produces a brick-red colour associated with haemolysis in severe cases; ethanol causes no specific lividity colour change.
Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.
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Written and medically reviewed by the StethoPrep medical team.