Forensic Pathology Practice Questions

Q: Which enzyme is responsible for converting ethanol to acetaldehyde in alcohol metabolism?

Alcohol dehydrogenase. ***Alcohol dehydrogenase*** - This is the **primary cytosolic enzyme** in hepatocytes responsible for the oxidation of **ethanol to acetaldehyde**. - The reaction involves the reduction of **NAD+ to NADH**, which contributes to the altered redox state in chronic alcohol consumption. *Aldehyde dehydrogenase* - This enzyme acts on the **second step** of alcohol metabolism, converting toxic **acetaldehyde into acetate**. - Inhibition of this enzyme by drugs like **Disulfiram** leads to an accumulation of acetaldehyde, causing unpleasant physical reactions. *Catalase* - Located within **peroxisomes**, this enzyme plays only a **minor role** (less than 2%) in hepatic alcohol metabolism. - It converts ethanol to acetaldehyde using **hydrogen peroxide**, primarily becoming relevant in the brain or under specific physiological conditions. *Cytochrome P450 2E1* - This enzyme is part of the **Microsomal Ethanol Oxidizing System (MEOS)** and is typically induced during **chronic heavy drinking**. - While it converts ethanol to acetaldehyde, it is not the primary enzyme in standard metabolism and generates **reactive oxygen species (ROS)** that contribute to liver injury.

Q: A 20-year-old male was found dead at home. His family claimed the cause of death was sudden myocardial infarction. What is the best test to distinguish an antemortem clot from a post-mortem clot?

Lines of Zahn. **Explanation:** The distinction between an antemortem thrombus and a post-mortem clot is a classic high-yield topic in forensic pathology. **1. Why "Lines of Zahn" is correct:** Lines of Zahn are the hallmark of a thrombus formed in **flowing blood** (antemortem). They consist of alternating pale layers (platelets and fibrin) and dark layers (red blood cells). Their presence signifies that the heart was still pumping at the time of formation, providing definitive evidence that the clot is antemortem. **2. Why the other options are incorrect:** * **B. Chicken fat appearance:** This is a characteristic of **post-mortem clots**. When blood settles after death, RBCs sediment due to gravity, leaving a clear, yellowish supernatant of plasma/fibrin (the "chicken fat" layer) above a dark red "currant jelly" layer. * **C & D. Red and White blood cells:** Both antemortem and post-mortem clots contain these cellular components. Their mere presence does not help in timing the clot; it is the **structural arrangement** (lamination) that matters. **Clinical Pearls for NEET-PG:** * **Antemortem Clot (Thrombus):** Firm, friable, dry, and **adherent** to the vessel wall. If pulled away, it leaves a damaged endothelial surface. * **Post-mortem Clot:** Soft, gelatinous, rubbery, and **not adherent** to the vessel wall (it forms a "cast" of the vessel and can be easily pulled out). * **Sudden Cardiac Death (SCD):** In young adults, while MI is possible, always consider Hypertrophic Cardiomyopathy (HCM) or Arrhythmogenic Right Ventricular Dysplasia (ARVD) as differentials in forensic scenarios.

Question 1

Which enzyme is responsible for converting ethanol to acetaldehyde in alcohol metabolism?

Accepted Answer

Alcohol dehydrogenase

Answer

Aldehyde dehydrogenase

Answer

Catalase

Answer

Cytochrome P450 2E1

Question 2

A 20-year-old male was found dead at home. His family claimed the cause of death was sudden myocardial infarction. What is the best test to distinguish an antemortem clot from a post-mortem clot?

Accepted Answer

Lines of Zahn

Answer

Chicken fat appearance

Answer

Red blood cells

Answer

White blood cells

Forensic Pathology — MCQs

Forensic Pathology — MCQs

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