Forensic Toxicology Practice Questions

Q: Which of the following is FALSE about Hydrocyanic acid?

Also called as muriatic acid. **Explanation** **1. Why Option A is the Correct Answer (The False Statement):** Hydrocyanic acid (HCN) is commonly known as **Prussic acid**. The term **Muriatic acid** refers to **Hydrochloric acid (HCl)**. This is a common nomenclature trap in forensic toxicology. **2. Analysis of Other Options:** * **Option B (Treatment):** The standard treatment for cyanide poisoning involves the "Cyanide Antidote Kit." **Amyl nitrite** (inhaled) and **Sodium nitrite** (IV) are used to induce methemoglobinemia. Methemoglobin has a high affinity for cyanide, forming cyanmethemoglobin, which prevents cyanide from binding to cellular enzymes. **Sodium thiosulfate** is then administered to convert cyanide into non-toxic thiocyanate. * **Option C (Mechanism):** Cyanide is a potent cellular toxin. It binds to the ferric ($Fe^{3+}$) iron of **cytochrome oxidase $a_3$** in the mitochondrial electron transport chain. This inhibits aerobic respiration, leading to "histotoxic hypoxia." * **Option D (Sequelae):** Survivors of severe cyanide poisoning may develop delayed neurological damage. The basal ganglia (specifically the putamen) are highly sensitive to cyanide-induced hypoxia, which can manifest clinically as **Parkinsonism** or dystonia. **Clinical Pearls for NEET-PG:** * **Odor:** Characteristically described as **"Bitter Almonds"** (present in only ~60% of the population due to genetics). * **Post-mortem finding:** The skin and viscera often show a **bright cherry-red** discoloration due to high levels of oxyhemoglobin (as tissues cannot utilize oxygen). * **Fatal Dose:** Approximately 50–100 mg of HCN; Fatal period is very short (2–10 minutes). * **Hydroxocobalamin (Cyanokit):** Now considered a first-line antidote as it binds cyanide to form Vitamin B12 (cyanocobalamin) without inducing methemoglobinemia.

Q: A 10-year-old girl was admitted to the emergency room with a history of ingesting 10 crushed seeds of an unknown plant. Her ECG showed specific abnormalities. What is the probable cause of these ECG changes?

Yellow oleander seeds. ***Yellow oleander seeds*** - Contains **cardiac glycosides** (thevetin A and thevetin B) that cause **digoxin-like ECG changes** including bradycardia, AV blocks, and ST scooping. - Approximately **10 seeds represent a lethal dose** in a child, making ECG abnormalities pathognomonic for cardiac glycoside poisoning. *Strychnine seeds* - Primarily affects the **central nervous system** causing **tetanic convulsions** and muscle spasms, not cardiac arrhythmias. - ECG changes are typically secondary to **hypoxia** from respiratory muscle paralysis, not direct cardiac toxicity. *Abrus precatorius seeds* - Contains **abrin toxin** that causes **severe gastroenteritis** and cellular toxicity affecting multiple organ systems. - Does not produce specific **cardiac glycoside-like ECG changes** but may cause secondary cardiac effects from fluid loss. *Ricinus communis seeds* - Contains **ricin toxin** leading to **gastrointestinal hemorrhage** and multi-organ failure through ribosomal protein synthesis inhibition. - Cardiac effects are secondary to **systemic toxicity** rather than direct cardiac glycoside activity on the heart.

Q: Two individuals presented with symptoms and subsequently died. A distinctive smell of bitter almonds was noted emanating from their mouths. These deaths are suspected to be due to which poison?

Hydrogen Cyanide. **Explanation:** The correct answer is **Hydrogen Cyanide (B)**. The "bitter almond" odor is a classic, high-yield clinical sign pathognomonic for cyanide poisoning. Cyanide acts as a potent cytotoxic hypoxia agent by binding to the ferric ($Fe^{3+}$) iron of **cytochrome oxidase a3** in the electron transport chain. This inhibits cellular respiration, leading to rapid death despite adequate oxygen saturation in the blood. **Analysis of Options:** * **Organophosphorus (A):** These compounds typically present with a characteristic **garlic-like or kerosene-like odor**. Clinical features include cholinergic crisis (miosis, salivation, lacrimation, and bradycardia). * **Aconite (C):** Known as "Sweet Poison" or "Blue Rocket," it does not have a specific diagnostic odor. It primarily causes tingling/numbness and fatal cardiac arrhythmias. * **Opium (D):** Opium and its derivatives are associated with a **smell of dried sweat or a "musty" odor**. Clinical signs include pinpoint pupils and respiratory depression. **NEET-PG High-Yield Pearls:** * **Post-mortem findings in Cyanide:** The skin and viscera often show a **bright cherry-red** discoloration due to the presence of excess oxyhemoglobin (as tissues cannot utilize oxygen). * **Genetic Note:** The ability to detect the bitter almond smell is genetically determined; approximately 20-40% of the population is "smell-blind" to cyanide. * **Other Odors to Remember:** * **Rotten Eggs:** Hydrogen Sulfide ($H_2S$). * **Shoe Polish/Nitrobenzene:** Nitrobenzene. * **Fishy/Musty:** Zinc Phosphide (due to Phosphine gas).

Q: A middle-aged man presents with paresthesia of the hands and feet. Examination reveals 'Mees' lines in the nails and raindrop pigmentation on the hands. What is the most likely causative toxin for these symptoms?

Arsenic. ### Explanation The clinical presentation of **paresthesia**, **Mees' lines**, and **raindrop pigmentation** is a classic triad indicative of **Chronic Arsenic Poisoning** (Arsenicism). 1. **Why Arsenic is Correct:** Arsenic is a protoplasmic poison that interferes with cell enzymes and sulfhydryl groups. * **Raindrop Pigmentation:** This refers to hyperpigmented spots interspersed with small areas of hypopigmentation, typically seen on the trunk and extremities. * **Mees' Lines:** These are transverse white bands across the nails caused by arsenic deposition in the keratin. * **Neuropathy:** Arsenic causes a symmetrical peripheral neuropathy (paresthesia) that often mimics Guillain-Barré syndrome. 2. **Why Other Options are Incorrect:** * **Lead:** Characterized by "Burtonian lines" (blue-grey lines on gums), wrist drop/foot drop, and basophilic stippling of RBCs, but not raindrop pigmentation. * **Thallium:** While it causes painful neuropathy and Mees' lines, its hallmark feature is **alopecia** (hair loss), which is absent here. * **Mercury:** Chronic poisoning (Hydrargyrism) presents with tremors (Danbury tremors), erethism (behavioral changes), and acrodynia (pink disease), but not the specific dermatological findings mentioned. ### High-Yield Clinical Pearls for NEET-PG: * **Arsenic Source:** Often associated with contaminated groundwater or smelting industries. * **Hyperkeratosis:** Thickening of the palms and soles (arsenical keratosis) is another pathognomonic sign. * **Garlic Odor:** The breath and stools of a patient with acute arsenic poisoning often smell of garlic. * **Treatment:** The drug of choice for chronic arsenic poisoning is **British Anti-Lewisite (BAL/Dimercaprol)** or **DMSA (Succimer)**. * **Sample for Diagnosis:** In chronic cases, **hair and nails** are the best samples because arsenic replaces phosphorus in keratin.

Q: A 40-year-old man, working in a farm, presented with headache, malaise, a sense of tightness, and dimness of vision. On examination, pupils were shown as below. What is the diagnosis?

Organophosphate poisoning. ***Organophosphate poisoning*** - Farm worker with **headache**, **malaise**, and **miosis** (pinpoint pupils) indicates **cholinergic toxidrome** from **acetylcholinesterase inhibition** by organophosphate pesticides. - Classic presentation includes **SLUDGE syndrome** (Salivation, Lacrimation, Urination, Defecation, Gastrointestinal distress, Emesis) with **muscarinic** and **nicotinic** effects. *Lead poisoning* - Causes **chronic neurological symptoms** like **peripheral neuropathy**, **wrist drop**, and **cognitive impairment** rather than acute cholinergic crisis. - Pupils are typically **normal** or may show **papilledema** in severe cases, not the characteristic **miosis** seen here. *Nickel poisoning* - Primarily causes **respiratory symptoms** like **asthma**, **pneumonitis**, and **dermatitis** from occupational exposure. - Does **not cause pupillary changes** or the acute neurological symptoms described in this case. *Cocaine poisoning* - Causes **sympathetic stimulation** leading to **mydriasis** (dilated pupils), **hypertension**, and **tachycardia**. - Neurological effects include **agitation**, **seizures**, and **hyperthermia**, opposite to the **cholinergic depression** seen here.

Q: A factory worker presented with tremors, personality change, and a blue line in the gum. What is the probable diagnosis of chronic poisoning with?

Mercury. This question tests your ability to differentiate between heavy metal poisonings that present with similar clinical signs, specifically the "blue line" on the gums. ### **Explanation of the Correct Answer** The correct answer is **Mercury (Chronic Poisoning/Hydrargyrism)**. While a blue line on the gums is classically associated with Lead, it also occurs in chronic Mercury poisoning (known as the **Burtonian line** or mercurial line). The diagnosis is confirmed by the presence of **tremors** and **personality changes**: * **Tremors:** Known as "Danbury tremors" or "Glass-blower's tremors." They are intention tremors affecting the hands, tongue, and eyelids. * **Personality Changes:** Known as **Erethism** (or "Mad Hatter syndrome"). Symptoms include irritability, pathological shyness, loss of memory, and insomnia. ### **Why Other Options are Incorrect** * **Lead (A):** While Lead poisoning causes a prominent blue line (Burton’s line) due to lead sulfide deposition, the classic triad includes abdominal colic, constipation, and peripheral motor neuropathy (wrist drop), rather than the specific psychiatric "Erethism" seen in Mercury. * **Arsenic (C):** Chronic arsenic poisoning presents with "raindrop" pigmentation of the skin, hyperkeratosis of palms/soles, and **Mees' lines** on the nails. It does not typically cause a blue gum line. * **Thallium (D):** The hallmark of Thallium poisoning is **alopecia** (hair loss) and painful peripheral neuropathy. ### **High-Yield Clinical Pearls for NEET-PG** * **Mercury Triad:** Tremors, Erethism, and Gingivitis/Stomatitis. * **Acrodynia (Pink Disease):** An idiosyncratic reaction to mercury in children (pinkish rash, peeling skin). * **Mercurentis:** Brownish discoloration of the anterior capsule of the lens. * **Lead vs. Mercury:** If the question mentions "Wrist drop/Colic," think **Lead**. If it mentions "Tremors/Erethism," think **Mercury**.

Q: Minamata Bay disease refers to chronic toxicity with which substance?

Mercury. **Explanation:** **Minamata Bay disease** is a neurological syndrome caused by chronic poisoning with **Methylmercury** (organic mercury). The disease was first discovered in 1956 in Minamata City, Japan, where industrial wastewater containing methylmercury was discharged into the bay. The mercury bioaccumulated in fish and shellfish, which were then consumed by the local population. **Why Mercury is Correct:** Chronic organic mercury poisoning primarily affects the Central Nervous System. Clinical features include the classic triad of **ataxia, constricted visual fields (tunnel vision), and paresthesia**. It can also cause hearing loss and dysarthria. In utero exposure leads to "Congenital Minamata Disease," resembling cerebral palsy. **Why Other Options are Incorrect:** * **Ergot:** Chronic poisoning (Ergotism) results from consuming grain infected with *Claviceps purpurea*. It presents as **St. Anthony’s Fire**, characterized by intense burning pain and dry gangrene of the extremities due to vasoconstriction. * **Dhatura:** An alkaloid poison (atropine/hyoscine) causing anticholinergic effects. Chronic toxicity is rare; acute poisoning presents with the "5 Ds": Dryness of mouth, Dysphagia, Dilated pupils, Delirium, and Death. * **Organophosphorus (OPC):** These inhibit acetylcholinesterase. Chronic exposure or sequelae include **OPIDN** (Organophosphate-Induced Delayed Neuropathy), but it is not associated with Minamata disease. **High-Yield Clinical Pearls for NEET-PG:** * **Pink Disease (Acrodynia):** Idiosyncratic reaction to mercury in children (presents with pinkish discoloration of hands/feet). * **Hunter-Russell Syndrome:** Another term for the neurological manifestations of organic mercury poisoning. * **Erethism (Mad Hatter Syndrome):** Characterized by irritability, shyness, and tremors, seen in chronic elemental mercury vapor inhalation. * **Danbury Tremor:** Coarse tremors seen in mercury toxicity.

Q: Respiratory center depression is caused by all except?

Strychnine. **Explanation:** The correct answer is **Strychnine**. The fundamental concept here is the distinction between **Central Nervous System (CNS) Depressants** and **CNS Stimulants**. 1. **Why Strychnine is the correct answer:** Strychnine is a potent spinal stimulant. It acts by competitively inhibiting **Glycine**, an inhibitory neurotransmitter, at the postsynaptic receptor sites in the spinal cord and medulla. By blocking inhibition, it causes uncontrolled neuronal excitation. This leads to generalized muscle spasms and convulsions (e.g., opisthotonus). Death usually occurs due to **asphyxia** caused by the *spastic* contraction of the diaphragm and thoracic muscles, rather than depression of the respiratory center itself. 2. **Why the other options are incorrect:** * **Opium:** A classic CNS depressant. It acts on mu-opioid receptors in the brainstem, directly reducing the sensitivity of the respiratory center to carbon dioxide, leading to fatal respiratory depression. * **Barbiturates:** These are sedative-hypnotics that enhance GABAergic inhibition. In toxic doses, they cause profound depression of the medullary respiratory center. * **Gelsemium:** Known as "Yellow Jasmine," it contains alkaloids like gelsemine that act as potent depressants of the anterior horn cells and the respiratory center, leading to respiratory failure. **High-Yield Clinical Pearls for NEET-PG:** * **Strychnine Sign:** Look for "Risus Sardonicus" (fixed grin) and "Opisthotonus" (arch-like bowing of the back). * **Post-mortem finding:** Rigor mortis appears and disappears very early in Strychnine poisoning due to exhaustion of ATP during convulsions. * **Antidote:** There is no specific antidote for Strychnine; management involves Diazepam (to control spasms) and maintaining a quiet, dark environment to prevent triggering seizures.

Q: Hypocalcemia is seen in poisoning of which substance?

Oxalic acid. **Explanation:** **Oxalic Acid (Correct Answer):** The hallmark of oxalic acid poisoning is **hypocalcemia**. Once absorbed, oxalic acid reacts with the calcium ions in the blood to form **insoluble calcium oxalate crystals**. This rapid depletion of ionized calcium leads to acute hypocalcemia, which can manifest clinically as tetany, muscle spasms, and cardiac arrhythmias. Furthermore, these calcium oxalate crystals precipitate in the renal tubules, leading to acute tubular necrosis and renal failure (oxaluria). **Incorrect Options:** * **Ammonia:** Poisoning typically causes severe mucosal burns, respiratory distress, and metabolic alkalosis, but it does not directly chelate calcium. * **Salicylates:** Aspirin overdose characteristically causes a mixed acid-base disturbance (early respiratory alkalosis followed by high anion gap metabolic acidosis) and hypoglycemia, but not primary hypocalcemia. * **Carbolic Acid (Phenol):** Phenol is a corrosive and a systemic toxin that causes "Ochronosis" (darkening of tissues) and "Carboluria" (greenish-black urine), but its primary mechanism does not involve calcium chelation. **Clinical Pearls for NEET-PG:** * **Antidote:** The specific treatment for oxalic acid poisoning is **Calcium Gluconate** (10% IV) to replenish calcium levels and precipitate the acid in the gut before absorption. * **Post-mortem finding:** "Coffee-ground" vomitus (due to acid hematin) and the presence of envelope-shaped calcium oxalate crystals in the kidneys. * **Common Source:** Often found in rust removers, metal polishes, and ink eradicators. It is sometimes called "Sugar of Salt."

Question 1

Which of the following is FALSE about Hydrocyanic acid?

Accepted Answer

Also called as muriatic acid

Answer

Sodium nitrite and amyl nitrite are used in treatment

Answer

Inhibits cytochrome oxidase

Answer

Delayed neurological sequel can develop in the form of Parkinson's disease

Question 2

A 10-year-old girl was admitted to the emergency room with a history of ingesting 10 crushed seeds of an unknown plant. Her ECG showed specific abnormalities. What is the probable cause of these ECG changes?

Accepted Answer

Yellow oleander seeds

Answer

Strychnine seeds

Answer

Abrus precatorius seeds

Answer

Ricinus communis seeds

Question 3

Two individuals presented with symptoms and subsequently died. A distinctive smell of bitter almonds was noted emanating from their mouths. These deaths are suspected to be due to which poison?

Accepted Answer

Hydrogen Cyanide

Answer

Organophosphorus

Answer

Aconite

Answer

Opium

Question 4

A middle-aged man presents with paresthesia of the hands and feet. Examination reveals 'Mees' lines in the nails and raindrop pigmentation on the hands. What is the most likely causative toxin for these symptoms?

Accepted Answer

Arsenic

Answer

Lead

Answer

Thallium

Answer

Mercury

Question 5

A 40-year-old man, working in a farm, presented with headache, malaise, a sense of tightness, and dimness of vision. On examination, pupils were shown as below. What is the diagnosis?

Accepted Answer

Organophosphate poisoning

Answer

Lead poisoning

Answer

Nickel poisoning

Answer

Cocaine poisoning

Question 6

A factory worker presented with tremors, personality change, and a blue line in the gum. What is the probable diagnosis of chronic poisoning with?

Accepted Answer

Mercury

Answer

Lead

Answer

Arsenic

Answer

Thallium

Question 7

Minamata Bay disease refers to chronic toxicity with which substance?

Accepted Answer

Mercury

Answer

Ergot

Answer

Dhatura

Answer

Organophosphorus

Question 8

Soot in the trachea is a sign of?

Accepted Answer

Cyanide poisoning

Answer

Postmortem burns

Answer

Antemortem burns

Answer

CO poisoning

Question 9

Respiratory center depression is caused by all except?

Accepted Answer

Strychnine

Answer

Opium

Answer

Barbiturates

Answer

Gelsemium

Question 10

Hypocalcemia is seen in poisoning of which substance?

Accepted Answer

Oxalic acid

Answer

Ammonia

Answer

Salicylates

Answer

Carbolic acid

Forensic Toxicology — MCQs

Forensic Toxicology — MCQs

On this page

Practice by Chapter

Want unlimited practice?