Forensic Toxicology — MCQs
On this page
Itai Itai disease is caused by toxicity of:
What is the characteristic color of post-mortem staining (livor mortis) seen in carbon monoxide poisoning?
Which substance is known to cause hepatotoxicity when ingested in excess?
Which of the following is a spinal poison?
Which of the following tests are used for arsenic poisoning?
Which poison has only a local action?
Green colored urine is seen in poisoning by which of the following?
What condition is characterized by chocolate cyanosis?
Intermediate muscle power loss is associated with poisoning due to which of the following?
Scorpion venom resembles the venom of which of the following?
Forensic Toxicology Indian Medical PG Practice Questions and MCQs
Question 461: Itai Itai disease is caused by toxicity of:
- A. Cadmium (Correct Answer)
- B. Antimony
- C. Lead
- D. Mercury
Explanation: **Explanation:** **Itai-Itai disease** is a chronic condition caused by long-term **Cadmium (Cd)** poisoning. The term, which translates to "ouch-ouch" disease, was coined in Japan in the 1950s following mass contamination of the Jinzū River. **Why Cadmium is Correct:** Cadmium toxicity primarily affects the proximal renal tubules, leading to severe renal dysfunction (Fanconi-like syndrome). This results in the excessive loss of calcium and phosphate in the urine, leading to **osteomalacia** (softening of bones) and **osteoporosis**. Patients suffer from multiple pathological fractures and intense bone pain, giving the disease its name. **Analysis of Incorrect Options:** * **Antimony:** Toxicity typically presents with gastrointestinal distress, metallic taste, and myocardial depression, but it does not cause bone softening or Itai-Itai disease. * **Lead:** Chronic lead poisoning (Plumbism) is characterized by the "ABCDEF" mnemonic: Anemia (basophilic stippling), Burtonian lines (blue gums), Colic, Dorsiflexion paralysis (wrist/foot drop), Encephalopathy, and Facies (pallor). * **Mercury:** Chronic toxicity causes **Minamata disease** (neurological syndrome), Erethism (abnormal irritability), and Acrodynia (Pink disease). **High-Yield Clinical Pearls for NEET-PG:** * **Source:** Cadmium is found in rechargeable batteries, pigments, and cigarette smoke. * **Diagnosis:** Elevated urinary β2-microglobulin is a sensitive marker for cadmium-induced renal tubular damage. * **Key Triad of Itai-Itai:** Osteomalacia, Renal tubular dysfunction, and severe bone pain. * **Treatment:** Chelation with EDTA may be used, though prevention of exposure is primary.
Question 462: What is the characteristic color of post-mortem staining (livor mortis) seen in carbon monoxide poisoning?
- A. Deep blue
- B. Bark brown
- C. Bright red
- D. Cherry red (Correct Answer)
Explanation: **Explanation:** The characteristic **cherry red** color of post-mortem staining in carbon monoxide (CO) poisoning is due to the formation of **carboxyhemoglobin (COHb)**. Carbon monoxide has an affinity for hemoglobin that is 200–250 times greater than that of oxygen. When inhaled, it binds stably to hemoglobin, preventing oxygen transport and shifting the oxygen-dissociation curve to the left. Carboxyhemoglobin is a stable, bright red compound that persists after death, imparting the classic cherry-red hue to the skin, mucous membranes, and internal organs. **Analysis of Incorrect Options:** * **Deep blue:** This represents cyanosis, typically seen in deaths due to asphyxia or heart failure, where there is an excess of deoxygenated hemoglobin. * **Dark brown:** This is characteristic of **Methemoglobinemia** (caused by nitrites, aniline dyes, or potassium chlorate) or phosphorus poisoning. * **Bright red:** While similar, "bright red" is more specifically associated with **Hydrocyanic acid (Cyanide)** poisoning (due to high oxyhemoglobin levels in venous blood) or exposure to extreme cold (hypothermia). **High-Yield NEET-PG Pearls:** * **Minimum COHb level** for cherry red staining to be visible: **30%**. * **Differential Diagnosis of PM Lividity Colors:** * **Cherry Red:** Carbon Monoxide. * **Bright Red/Pink:** Cyanide, Hypothermia. * **Chocolate/Dark Brown:** Nitrites, Potassium Chlorate, Nitrobenzene. * **Blue-Gray:** Silver salts (Argyria). * **Black:** Opium (due to intense congestion/asphyxia). * **Spectroscopic examination** is the most reliable method to detect carboxyhemoglobin in the blood.
Question 463: Which substance is known to cause hepatotoxicity when ingested in excess?
- A. Opium
- B. Cannabis
- C. Cocaine
- D. Alcohol (Correct Answer)
Explanation: **Explanation:** **Correct Answer: D. Alcohol** Alcohol (Ethanol) is a potent hepatotoxin. Its metabolism primarily occurs in the liver via the enzyme **Alcohol Dehydrogenase (ADH)**, which converts ethanol to **Acetaldehyde**, a highly reactive and toxic metabolite. Acetaldehyde causes oxidative stress, lipid peroxidation, and DNA damage. Chronic ingestion leads to a predictable spectrum of liver injury: **Steatosis** (fatty liver), **Alcoholic Hepatitis**, and eventually **Cirrhosis**. In forensic autopsies, a "nutmeg liver" appearance may be noted due to chronic venous congestion associated with cardiac failure or advanced cirrhosis. **Why other options are incorrect:** * **A. Opium:** Opioids primarily act on the CNS and respiratory system. The classic triad of poisoning includes coma, pinpoint pupils, and respiratory depression. They do not have direct hepatotoxic effects. * **B. Cannabis:** The active ingredient, THC, is metabolized by the liver but is not hepatotoxic. Toxicity typically manifests as tachycardia, conjunctival injection, and psychiatric symptoms (acute panic or psychosis). * **C. Cocaine:** While cocaine is a powerful sympathomimetic that causes vasoconstriction, hypertension, and myocardial infarction, it is not primarily known for hepatotoxicity. Its main forensic significance lies in sudden cardiac death and intracranial hemorrhage. **High-Yield Clinical Pearls for NEET-PG:** * **Mallory-Denk bodies:** Eosinophilic cytoplasmic inclusions found in hepatocytes, characteristic of alcoholic hepatitis. * **AST:ALT Ratio:** In alcoholic liver disease, the ratio is typically **>2:1**. * **GGT (Gamma-Glutamyl Transferase):** The most sensitive biochemical marker for chronic alcohol consumption. * **Other Hepatotoxic substances to remember:** Paracetamol (Acetaminophen), Carbon tetrachloride ($CCl_4$), Phosphorus, and *Amanita phalloides* mushrooms.
Question 464: Which of the following is a spinal poison?
- A. Strychnine (Correct Answer)
- B. Organophosphorus
- C. Oleander
- D. Cannabis
Explanation: **Explanation:** **Strychnine** (derived from *Strychnos nux-vomica*) is the classic example of a **spinal poison**. It acts by competitively inhibiting **Glycine**, an inhibitory neurotransmitter, at the postsynaptic receptor sites in the anterior horn cells of the spinal cord. This removal of post-synaptic inhibition leads to excessive stimulation of the motor neurons, resulting in characteristic violent, involuntary muscle spasms (opisthotonus). **Analysis of Incorrect Options:** * **Organophosphorus (OPC):** These are **Agricultural/Neurotoxic poisons** that inhibit Acetylcholinesterase, leading to a cholinergic crisis (DUMBELS). They act primarily at the neuromuscular junction and autonomic nervous system, not specifically the spinal cord. * **Oleander:** This is a **Cardiac poison**. It contains glycosides (like oleandrin) that act similarly to Digoxin, affecting the sodium-potassium pump of the myocardium, leading to arrhythmias. * **Cannabis:** This is a **Deliriant/Hallucinogenic poison** (Cerebral poison). It acts on the CNS (CB1 and CB2 receptors) to alter perception, mood, and consciousness. **High-Yield Clinical Pearls for NEET-PG:** * **Risus Sardonicus:** A characteristic "sardonic smile" seen in Strychnine poisoning due to spasms of facial muscles (also seen in Tetanus). * **Differential Diagnosis:** Unlike Tetanus, Strychnine poisoning has a rapid onset, and muscles are **completely relaxed between convulsions**. * **Post-mortem finding:** Rigor mortis appears and disappears very early due to the exhaustion of ATP from severe convulsions. * **Fatal Dose:** 30–100 mg of Strychnine; Fatal period is 1–2 hours.
Question 465: Which of the following tests are used for arsenic poisoning?
- A. Marsh's test
- B. Reinsch's test
- C. Macewan's test
- D. Marqui's test (Correct Answer)
Explanation: **Explanation:** The question asks to identify the test used for **Arsenic poisoning**. However, based on standard forensic toxicology, there appears to be a discrepancy in the provided key. **Marsh’s test** and **Reinsch’s test** are the classic diagnostic tests for Arsenic, while **Marquis test** is used for Opioids. **1. Why the Options are Significant:** * **Marsh’s Test (Option A):** This is the **most delicate and definitive** qualitative test for arsenic. It involves the formation of arsine gas, which, when heated, deposits a "silvery-black mirror" of elemental arsenic on a cool porcelain surface. * **Reinsch’s Test (Option B):** A rapid screening test used for heavy metals (Arsenic, Mercury, Antimony, Bismuth). A copper foil is placed in a solution of the suspected material and HCl; a steel-grey/black deposit indicates arsenic. * **Marquis Test (Option D - Marked Correct):** This is a colorimetric field test used to identify **Alkaloids**, specifically **Opioids** (Morphine/Heroin) and Amphetamines. It turns **purple/violet** in the presence of morphine. *Note: If this is the intended answer for Arsenic in a specific exam context, it is likely a clerical error in the question paper.* * **Macewan’s Sign (Option C):** This is a clinical sign (cracked-pot sound on percussion of the skull) seen in hydrocephalus or brain abscess, not a toxicological test. **High-Yield Clinical Pearls for Arsenic:** * **Acute Poisoning:** Presents with "Rice water stools" (mimics Cholera). * **Chronic Poisoning (Arsenicosis):** Look for **Raindrop pigmentation**, **Aldrich-Mees lines** (transverse white bands on nails), and hyperkeratosis of palms/soles. * **Antidote:** BAL (British Anti-Lewisite) or Dimercaprol. * **Post-mortem:** Arsenic retards putrefaction (mummification).
Question 466: Which poison has only a local action?
- A. Sulphuric acid (Correct Answer)
- B. Carbolic acid
- C. Oxalic acid
- D. Phosphorus
Explanation: **Explanation:** Corrosive poisons are classified based on their mechanism of action into those with **local action** only and those with **remote/systemic effects**. **1. Why Sulphuric Acid is Correct:** Sulphuric acid is a strong mineral acid that acts as a powerful **dehydrating agent**. Upon contact with tissues, it causes immediate **coagulative necrosis**, charring (carbonization), and intense local destruction. It does not get absorbed into the systemic circulation in a form that causes specific organ toxicity elsewhere; its morbidity and mortality are entirely due to the local chemical burns, perforation of the GI tract, and subsequent shock or scarring (strictures). **2. Analysis of Incorrect Options:** * **Carbolic Acid (Phenol):** Known as a "local anesthetic" corrosive, it is rapidly absorbed through the skin and mucous membranes, leading to CNS depression and renal failure (**Ochronosis**). It has both local and systemic actions. * **Oxalic Acid:** While it causes local irritation, its primary danger is systemic. It chelates serum calcium leading to **hypocalcemia** and forms calcium oxalate crystals in the renal tubules, causing **acute renal failure**. * **Phosphorus:** Acts as a local irritant but is notorious for its systemic effects on the liver (fatty degeneration) and heart. It is a classic protoplasmic poison. **Clinical Pearls for NEET-PG:** * **Vitriolage:** The act of throwing sulphuric acid on a person (Section 326A/326B IPC). * **Stomach Appearance:** In sulphuric acid poisoning, the stomach is often charred, black, and friable (**"Leather bottle"** appearance is more common in chronic cases, but acute perforation is a high risk). * **Exceptions:** Most mineral acids (Nitric, Hydrochloric) have primarily local actions, whereas organic acids (Oxalic, Carbolic) have significant systemic effects.
Question 467: Green colored urine is seen in poisoning by which of the following?
- A. Kerosene
- B. Organophosphate compounds
- C. Carbolic acid (Correct Answer)
- D. Paracetamol
Explanation: **Explanation:** The correct answer is **Carbolic Acid (Phenol)**. **Why Carbolic Acid is correct:** Carbolic acid poisoning characteristically causes **Carboluria**. When phenol is ingested or absorbed, it is metabolized in the liver and excreted in the urine as **quinol (hydroquinone) and pyrocatechol**. While the urine may appear normal when freshly voided, upon standing and exposure to air, these metabolites undergo oxidation to form colored compounds, giving the urine a characteristic **smoky green or dark green appearance**. **Analysis of Incorrect Options:** * **Kerosene:** Hydrocarbon poisoning typically presents with a kerosene-like odor on the breath and chemical pneumonitis. It does not cause specific discoloration of urine. * **Organophosphate compounds:** These inhibit acetylcholinesterase, leading to a cholinergic crisis (SLUDGE syndrome). While the urine may have a garlic-like odor, it does not turn green. * **Paracetamol:** Acute overdose leads to fulminant hepatic failure. While it can cause dark urine due to jaundice (bilirubinuria), it does not produce the green discoloration seen in phenol poisoning. **High-Yield Clinical Pearls for NEET-PG:** * **Smell of Carbolic Acid:** Characteristic "phenolic" or "hospital-like" odor. * **Ochronosis:** Chronic phenol poisoning can lead to brownish-black pigmentation of cartilages and connective tissues. * **Other causes of Green/Blue-Green Urine:** Methylene blue, Amitriptyline, Propofol, and *Pseudomonas* infection. * **Black Urine:** Seen in poisoning by Nitrites, Naphthalene, and sometimes late-stage Carbolic acid (due to excessive oxidation).
Question 468: What condition is characterized by chocolate cyanosis?
- A. Wilson's disease
- B. Zinc poisoning
- C. Methemoglobinemia (Correct Answer)
- D. Mercury poisoning
Explanation: **Explanation:** **Methemoglobinemia** is the correct answer. This condition occurs when the ferrous iron ($Fe^{2+}$) in hemoglobin is oxidized to the ferric state ($Fe^{3+}$). Ferric iron cannot bind oxygen, and its presence increases the oxygen affinity of the remaining ferrous hemes (shifting the dissociation curve to the left), leading to severe tissue hypoxia. The characteristic **"chocolate cyanosis"** refers to the dark, brownish-blue discoloration of the blood and skin that does not improve with supplemental oxygen. This is a classic finding in poisonings involving oxidizing agents like **nitrites, aniline dyes, acetanilide, and nitrobenzene.** **Analysis of Incorrect Options:** * **Wilson’s Disease:** Characterized by copper accumulation. Key findings include Kayser-Fleischer (KF) rings in the cornea and "Sunflower cataracts," not cyanosis. * **Zinc Poisoning:** Typically presents with gastrointestinal irritation or "Metal Fume Fever" (chills, fever, and malaise) if inhaled. It does not cause chocolate-colored blood. * **Mercury Poisoning:** Chronic exposure leads to **Erethism** (behavioral changes), **Acrodynia** (Pink disease), and tremors (Danbury tremor). It is not associated with methemoglobin formation. **High-Yield Clinical Pearls for NEET-PG:** * **Antidote:** The treatment of choice for symptomatic methemoglobinemia is **Methylene Blue** (1-2 mg/kg IV), which acts as a reducing agent. * **Diagnosis:** Suspect this when there is a "saturation gap" (low $SpO_2$ on pulse oximetry but normal $PaO_2$ on ABG). * **Post-mortem:** Blood remains chocolate-brown even after exposure to air, unlike normal deoxygenated blood which turns red.
Question 469: Intermediate muscle power loss is associated with poisoning due to which of the following?
- A. Barbiturates
- B. Carbon monoxide
- C. Cyanide
- D. Organophosphorous compounds (Correct Answer)
Explanation: **Explanation:** **Organophosphorous (OP) compounds** are the correct answer because they are uniquely associated with three distinct phases of paralysis. The **Intermediate Syndrome (IMS)**, also known as Type II paralysis, occurs typically 24–96 hours after the acute cholinergic crisis has subsided. It is characterized by a sudden loss of muscle power, specifically affecting the proximal limb muscles, neck flexors, and cranial nerves. The most critical complication of IMS is respiratory muscle paralysis, which often necessitates mechanical ventilation. The underlying mechanism is thought to be a combination of pre- and post-synaptic neuromuscular junction dysfunction due to prolonged acetylcholinesterase inhibition. **Incorrect Options:** * **Barbiturates:** These are CNS depressants. Toxicity typically presents with coma, respiratory depression, and "barbiturate blisters" (bullae), but not a specific "intermediate" muscle power loss phase. * **Carbon Monoxide:** Toxicity causes cellular hypoxia. Clinical features include cherry-red skin discoloration and Parkinsonian-like symptoms due to basal ganglia (globus pallidus) necrosis, rather than delayed muscle paralysis. * **Cyanide:** This is a potent cellular toxin that inhibits cytochrome oxidase. It causes rapid death via "histotoxic hypoxia." It does not feature a subacute muscle power loss syndrome. **High-Yield Clinical Pearls for NEET-PG:** * **OP Poisoning Triad:** Muscarinic effects (miosis, bradycardia, secretions), Nicotinic effects (fasciculations, weakness), and CNS effects. * **Three Phases of OP Paralysis:** 1. **Type I:** Acute cholinergic crisis (Nicotinic blockade). 2. **Type II (Intermediate Syndrome):** Occurs 1–4 days later; affects proximal muscles and neck flexors. 3. **Type III (OPIDN):** Delayed polyneuropathy occurring 2–3 weeks later due to inhibition of **Neuropathy Target Esterase (NTE)**; presents as "foot drop." * **Management:** Atropine (reverses muscarinic effects) and Pralidoxime/PAM (reactivates acetylcholinesterase if given before "aging" occurs).
Question 470: Scorpion venom resembles the venom of which of the following?
- A. Cobra
- B. Viper
- C. Krait
- D. All of the above (Correct Answer)
Explanation: **Explanation:** The correct answer is **D. All of the above**. Scorpion venom is a complex mixture of proteins and polypeptides that exhibits a multi-systemic toxic effect, effectively mimicking the clinical profiles of various venomous snakes. It contains **neurotoxins**, **cardiotoxins**, and **hemolysins**, which explains its resemblance to the following: * **Cobra (Option A):** Like cobra venom, scorpion venom contains potent neurotoxins that affect the central nervous system and can lead to respiratory paralysis. * **Viper (Option B):** Similar to viper venom, it contains hemolysins and local irritants that cause intense local pain, edema, and potential coagulopathy or vasculotoxicity. * **Krait (Option C):** Like krait venom, it has powerful neurotoxic components that can lead to autonomic storms and neuromuscular blockade. **Clinical Pearls for NEET-PG:** 1. **Mechanism of Action:** Scorpion venom acts primarily by prolonging the opening of **sodium channels**, leading to a massive release of endogenous catecholamines (the "Autonomic Storm"). 2. **Clinical Presentation:** This "sympathetic storm" results in hypertension, tachycardia, and the most common cause of death: **Acute Pulmonary Edema** and **Myocarditis**. 3. **Grading:** The **Mesilla Grading** is often used to assess the severity of scorpion stings. 4. **Treatment:** The drug of choice for managing the cardiovascular effects (hypertension and pulmonary edema) of a scorpion sting is **Prazosin** (an alpha-1 blocker), which acts as a physiological antagonist to the venom's effects.
Practice by Chapter
General Principles of Toxicology
Practice Questions
Corrosive Poisons
Practice Questions
Metallic Poisons
Practice Questions
Non-Metallic Poisons
Practice Questions
Organic Irritant Poisons
Practice Questions
Neurotic Poisons
Practice Questions
Cardiac Poisons
Practice Questions
Asphyxiant Poisons
Practice Questions
Food Poisoning
Practice Questions
Drug Abuse and Dependence
Practice Questions
Analytical Toxicology Methods
Practice Questions
Interpretation of Toxicology Results
Practice Questions
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free