Mercury Exposure — MCQs
A 3 yrs old child is brought to the emergency room by his parents after they found him having a generalized seizure at home. The child's breath smells of garlic, and he has bloody diarrhea, vomiting, and muscle twitching. Which poison is it likely that this child has encountered?
Which of the following statements about Wilson's disease is false?
An industrial worker presents with blue lines on gums and tremors. What is the most probable diagnosis?
What is the primary purpose of xenobiotic metabolism?
Mercury intoxication in a dental office mainly results from:
A 6-year-old boy is admitted to the ward with drowsiness, dull deep tendon reflexes and seizures. On examination the child has a line on gums and there is a history of constipation. Which will be most appropriate drug that should be used for this child?
Which of the following is most specific for arsenic poisoning ?
Which occupational exposure may cause sterility in females ?
Pink disease is seen due to
Which of the following is the recommended treatment for iron poisoning in a 4-year-old child?
Mercury Exposure Indian Medical PG Practice Questions and MCQs
Question 1: A 3 yrs old child is brought to the emergency room by his parents after they found him having a generalized seizure at home. The child's breath smells of garlic, and he has bloody diarrhea, vomiting, and muscle twitching. Which poison is it likely that this child has encountered?
- A. Thallium
- B. Carbon monoxide
- C. Arsenic (Correct Answer)
- D. Lead
Explanation: **Arsenic** - **Arsenic poisoning** in children can present with a combination of **gastrointestinal distress** (bloody diarrhea, vomiting) [1], **neurological symptoms** (seizures, muscle twitching) [1], [3], and a characteristic **garlic-like odor** on the breath [1]. - The rapid onset of severe symptoms, including seizures, is consistent with acute arsenic toxicity [3]. *Thallium* - **Thallium poisoning** typically presents with **hair loss**, painful **neuropathy**, and gastrointestinal upset. - A garlic odor on the breath and acute seizures as prominent initial symptoms are not characteristic of thallium exposure. *Carbon monoxide* - **Carbon monoxide poisoning** would present with symptoms like **headache**, **dizziness**, nausea, and **cherry-red skin** in severe cases, but not a garlic odor or bloody diarrhea. - **Seizures** can occur, but the overall clinical picture, especially the garlic breath and bloody diarrhea, is inconsistent. *Lead* - **Lead poisoning** in children is often chronic, presenting with neurodevelopmental issues, **abdominal pain** (lead colic), **anemia**, and a **"lead line" on the gums** [2]. - While seizures can be a late manifestation of severe lead encephalopathy [2], the acute presentation with garlic breath, bloody diarrhea, and rapid-onset seizures is not typical for lead exposure.
Question 2: Which of the following statements about Wilson's disease is false?
- A. Autosomal recessive
- B. Serum ceruloplasmin level < 20 mg/dl
- C. Urinary copper excretion < 100 micrograms/day (Correct Answer)
- D. Zinc acetate is used as maintenance therapy
Explanation: ***Urinary copper excretion < 100 micrograms/day*** - A definitive diagnostic criterion for Wilson's disease is an **elevated 24-hour urinary copper excretion**, typically **greater than 100 µg/day** (or occasionally 40-100 μg/day in symptomatic patients). - Therefore, a value *less than 100 µg/day* would be considered a normal finding and would indicate that Wilson's disease is unlikely, making this statement false in the context of diagnosing the disease. *Autosomal recessive* - Wilson's disease is inherited in an **autosomal recessive pattern**, meaning an individual must inherit two copies of the mutated *ATP7B* gene (one from each parent) to develop the disease. - This characteristic inheritance pattern is fundamental to understanding the genetic basis of the disorder. *Serum ceruloplasmin level < 20 mg/dl* - **Low serum ceruloplasmin** (typically < 20 mg/dL) is a hallmark of Wilson's disease, as ceruloplasmin is the major copper-carrying protein in the blood, and its synthesis is impaired. - This low level indicates defective copper metabolism and transport, leading to copper accumulation. *Zinc acetate is used as maintenance therapy* - **Zinc acetate** (e.g., Galzin) is a commonly used maintenance therapy for Wilson's disease. - It works by inducing **metallothionein** in enterocytes, which sequesters dietary copper and prevents its absorption, thereby promoting fecal copper excretion.
Question 3: An industrial worker presents with blue lines on gums and tremors. What is the most probable diagnosis?
- A. Mercury
- B. Lead (Correct Answer)
- C. Arsenic poisoning
- D. Carbon monoxide
Explanation: ***Lead*** - **Blue lines on the gums (Burton's lines)** are a classic symptom of chronic lead poisoning, caused by a reaction between circulating lead and sulfur ions released by oral bacteria [2]. - **Tremors** and other neurological symptoms like *wrist drop* or *foot drop* are common manifestations of lead's neurotoxic effects [1]. *Mercury* - While **tremors** are a prominent symptom of mercury poisoning, especially *finger tremors* and *erectile dysfunction*, **blue lines on the gums** are not characteristic [3]. - Mercury poisoning is often associated with **gingivitis**, **stomatitis**, and *Erythrism* (mad hatter disease), which involves psychological changes like irritability and shyness [3]. *Arsenic poisoning* - **Arsenic poisoning** can cause **neuropathy**, but **tremors** and **blue lines on the gums** are not typical features. - It classically presents with **rain drop skin pigmentation**, **hyperkeratosis**, and **Mees' lines** (transverse white bands on nails). *Carbon monoxide* - **Carbon monoxide poisoning** primarily affects the cardiovascular and central nervous systems, leading to symptoms like **headache**, **nausea**, and cherry-red skin coloration. - **Blue lines on the gums** and **tremors** are not associated with carbon monoxide toxicity.
Question 4: What is the primary purpose of xenobiotic metabolism?
- A. Increase water solubility (Correct Answer)
- B. Increase lipid solubility
- C. Make them nonpolar
- D. None of the above
Explanation: ***Increase water solubility*** - The primary goal of xenobiotic metabolism is to make these foreign compounds more **hydrophilic** (water-soluble). - This increased water solubility facilitates their **excretion** from the body via urine or bile. *Increase lipid solubility* - Increasing **lipid solubility** would make xenobiotics more likely to accumulate in **adipose tissue** and pass through cell membranes, hindering their excretion. - This is the opposite of the desired outcome for xenobiotic elimination. *Make them nonpolar* - Making xenobiotics **nonpolar** would be equivalent to increasing their lipid solubility, as nonpolar molecules tend to be lipid-soluble. - This would impede excretion and potentially lead to **bioaccumulation**, which is harmful. *None of the options* - This option is incorrect because xenobiotic metabolism specifically aims to increase **water solubility** for elimination.
Question 5: Mercury intoxication in a dental office mainly results from:
- A. Direct contact with the mercury
- B. Inhalation of mercury vapours (Correct Answer)
- C. Ingestion of mercury
- D. None of the options
Explanation: ***Inhalation of mercury vapours*** - In a dental office setting, **mercury vapors** are released during the mixing, placement, and removal of **dental amalgam** fillings. - **Inhaling these invisible and odorless vapors** is the primary route of **mercury absorption** into the body, leading to systemic toxicity. *Direct contact with the mercury* - While **skin contact** with mercury can lead to some absorption, it is generally considered a less significant route for systemic toxicity compared to inhalation in a dental environment. - The amount absorbed through the skin is usually **minor** unless prolonged and extensive exposure occurs, or if the mercury is in an organic form. *Ingestion of mercury* - **Ingestion of mercury** is uncommon in a dental office and typically involves accidental swallowing of amalgam particles or contaminated food/drink. - Although harmful, this route is **not the main mechanism** for chronic exposure and systemic intoxication in this professional setting. *None of the options* - This option is incorrect because the primary and most significant route of **mercury intoxication** in a dental office is indeed listed among the choices: **inhalation of mercury vapors**.
Question 6: A 6-year-old boy is admitted to the ward with drowsiness, dull deep tendon reflexes and seizures. On examination the child has a line on gums and there is a history of constipation. Which will be most appropriate drug that should be used for this child?
- A. EDTA
- B. DMSA (Correct Answer)
- C. BAL
- D. Penicillamine
Explanation: ***DMSA*** - The child's symptoms of **drowsiness**, **dull deep tendon reflexes**, **seizures**, a **gingival line**, and **constipation** are classic signs of **lead poisoning**. - **DMSA (dimercaptosuccinic acid)** is a chelating agent that is generally considered the **first-line treatment** for pediatric lead poisoning due to its oral administration, good safety profile, and efficacy in reducing lead levels. *Penicillamine* - While penicillamine is a chelating agent, it is **less commonly used** for lead poisoning in children due to a higher incidence of **side effects** compared to DMSA. - Its use is often reserved for patients who cannot tolerate other chelating agents or in specific situations. *EDTA* - **EDTA (ethylenediaminetetraacetic acid)** is a powerful chelator often used for severe lead poisoning, but it is typically administered **intravenously** or **intramuscularly**. - It is often combined with BAL to prevent redistribution of lead to the brain and is not usually the first choice for chronic, less severe lead poisoning in an ambulatory setting. *BAL* - **BAL (British Anti-Lewisite)**, or **dimercaprol**, is an oil-based intramuscular injection and is usually reserved for **severe lead encephalopathy**. - It has a high incidence of **adverse effects** and should not be used as monotherapy for lead poisoning due to the risk of redistributing lead to the brain; it is typically administered with EDTA for very high lead levels.
Question 7: Which of the following is most specific for arsenic poisoning ?
- A. Garlic-like odor in breath and urine (Correct Answer)
- B. Blue line on gums
- C. Tremors
- D. Anemia
Explanation: ***Garlic-like odor in breath and urine*** - A **garlic-like odor** in the breath and urine is a classic and highly **specific sign** of **arsenic poisoning**. - This distinctive odor is due to the **methylation of arsenic** compounds in the body. *Blue line on gums* - A **blue line on the gums**, also known as a **Burton line**, is characteristic of **lead poisoning**, not arsenic. - It results from the deposition of **lead sulfide** in the gingival tissue. *Tremors* - **Tremors** can be a symptom of various toxic exposures and neurological conditions, making them a **non-specific finding** for arsenic poisoning alone. - While **chronic arsenic poisoning** can lead to neurological symptoms, tremors are not a primary distinguishing feature. *Anemia* - **Anemia** is a common and **non-specific sign** that can be caused by many conditions, including various toxic exposures. - While chronic arsenic exposure can lead to **bone marrow suppression** and anemia, it is not specific enough for diagnosis.
Question 8: Which occupational exposure may cause sterility in females ?
- A. Agricultural insecticides
- B. Lead (Correct Answer)
- C. Mercury
- D. Carbon monoxide
Explanation: ***Lead*** - **Lead exposure** is a well-established occupational hazard causing **female sterility** and reproductive dysfunction - Occupational exposure occurs in **battery manufacturing**, lead smelting, paint industries, and pottery glazing - Lead affects the **hypothalamic-pituitary-ovarian axis**, causing **menstrual irregularities**, anovulation, and reduced fertility - Can lead to **spontaneous abortions**, **stillbirths**, and in chronic exposure, **sterility** - Classic textbook reference: **K. Park's Preventive and Social Medicine** lists lead as a cause of sterility in females *Mercury* - Mercury exposure (organic and inorganic forms) can affect reproductive health through **endocrine disruption** - More commonly associated with **neurological toxicity** (Minamata disease) than definitive sterility - Can cause menstrual disturbances and fertility issues, but **lead has stronger evidence** for causing sterility - Occupational exposure: dental workers, thermometer/fluorescent bulb manufacturing *Agricultural insecticides* - Some pesticides (organochlorines, organophosphates) act as **endocrine disruptors** - Can reduce fertility and cause menstrual irregularities - Rarely cause **complete sterility** unless there is severe acute poisoning - Effects are often **reversible** after cessation of exposure *Carbon monoxide* - Primarily causes tissue **hypoxia** by binding to hemoglobin - Not a **direct reproductive toxicant** causing sterility - Severe poisoning can affect various organs through oxygen deprivation, but this is not the mechanism of occupational sterility - Not classically associated with female sterility in occupational medicine
Question 9: Pink disease is seen due to
- A. Arsenic poisoning
- B. Internal resorption
- C. Trauma
- D. Mercury poisoning (Correct Answer)
Explanation: ***Mercury poisoning*** - **Pink disease**, also known as **acrodynia**, is a historical term for a childhood illness caused by chronic exposure to **mercury** [1]. - Symptoms include a characteristic pink rash on the hands and feet, irritability, photophobia, and hypotonia [1]. *Arsenic poisoning* - **Arsenic poisoning** can lead to symptoms like gastrointestinal distress, skin lesions (hyperkeratosis, melanosis), and neurological effects [2]. - It does not typically cause the characteristic pink rash and other signs associated with acrodynia. *Internal resorption* - **Internal resorption** is a dental condition where the dentin and cementum of a tooth are resorbed from within the pulp chamber or root canal. - This condition is localized to the tooth and is not associated with systemic symptoms or a widespread rash like pink disease. *Trauma* - **Trauma** refers to physical injury and can cause various localized or systemic effects depending on the nature and severity of the injury. - While trauma can lead to discoloration or rashes, it is not a direct cause of the specific syndrome known as pink disease (acrodynia).
Question 10: Which of the following is the recommended treatment for iron poisoning in a 4-year-old child?
- A. Blood transfusion
- B. Stomach lavage
- C. Observation and supportive care
- D. Deferoxamine IV at a dose of 15 mg/kg/hour (Correct Answer)
Explanation: ***Deferoxamine IV at a dose of 15 mg/kg/hour*** - **Deferoxamine** is a chelating agent specifically used to bind free iron, forming a complex that can be excreted renally. - An intravenous infusion at 15 mg/kg/hour is the recommended dose for severe iron poisoning, particularly when serum iron levels are high or symptoms indicate significant toxicity. *Stomach lavage* - **Stomach lavage** is generally not recommended for iron poisoning due to the risk of pushing iron tablets further into the intestine, potential for perforation, and limited efficacy in removing large, unabsorbed iron tablets. - Iron tablets are often **large** and **poorly soluble**, making lavage ineffective for complete removal. *Blood transfusion* - **Blood transfusion** is not a primary treatment for iron poisoning because iron toxicity is due to free iron in the body, not a deficiency that would be corrected by transfused blood. - It would only be considered in cases of severe anemia or significant blood loss, which are not direct treatments for iron overload. *Observation and supportive care* - While supportive care is crucial in managing complications of iron poisoning, **observation alone is insufficient** for moderate to severe cases of iron poisoning. - Significant iron overdose requires active intervention to prevent systemic toxicity, organ damage, and potentially fatal outcomes.
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