Autopsy of a case of cyanide poisoning shows all of the following features, EXCEPT:
## Core Concept
Cyanide poisoning is a condition characterized by the inhibition of cellular respiration, leading to a lack of oxygen utilization by tissues despite adequate oxygen delivery. This results in a significant increase in venous oxygen levels. The mechanism involves the binding of cyanide ions to the iron atom in cytochrome c oxidase (Complex IV) of the mitochondrial electron transport chain.
## Why the Correct Answer is Right
The correct answer, ., implies that the feature not typically associated with cyanide poisoning needs to be identified. In cyanide poisoning, autopsy findings often include a bright red or pink discoloration of the skin and mucous membranes due to high oxygen levels in the blood, and tissues may appear bright red due to increased venous oxygen. The cherry-red spot is a classic finding, particularly in the lips, tongue, and mucous membranes.
## Why Each Wrong Option is Incorrect
- **Option A:** Typically, cyanide poisoning results in a characteristic cherry-red discoloration of the skin and mucous membranes. This is due to the high levels of oxyhemoglobin in the venous blood. Therefore, option A is a feature associated with cyanide poisoning.
- **Option B:** The presence of a bitter almond smell from the breath or tissues can be a feature of cyanide poisoning, as cyanide compounds can release hydrogen cyanide gas, which has a characteristic bitter almond odor. Thus, option B is associated with cyanide poisoning.
- **Option C:** The finding of a significantly increased venous oxygen content or saturation is consistent with cyanide poisoning, as the tissues are unable to utilize oxygen. This would be reflected in autopsy findings. So, option C is also a feature of cyanide poisoning.
## Clinical Pearl / High-Yield Fact
A key clinical pearl in cyanide poisoning is the presence of a **cherry-red discoloration** of the skin, which is a classic but not universal finding. This occurs due to the increased amount of oxyhemoglobin in the venous blood. It's crucial to note that while this finding is suggestive, it's not pathognomonic, and the diagnosis relies heavily on clinical suspicion and laboratory confirmation.
**Correct Answer: .**