Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 1221: What is the most common cause of death following measles infection?

A. Diarrhea
B. SSPE
C. Myocarditis
D. Respiratory tract infections (RTIs) (Correct Answer)

Explanation: ***Respiratory tract infections (RTIs)*** - **Pneumonia**, a common complication of measles, is the leading cause of death, especially in young children and immunocompromised individuals [1]. - Measles causes **immunosuppression**, making individuals more susceptible to secondary bacterial and viral RTIs [1]. *Diarrhea* - While **diarrhea** is a common complication of measles, leading to dehydration and malnutrition, it is not the most frequent cause of death. - **Gastrointestinal complications** are more prevalent in malnourished populations. *SSPE* - **Subacute sclerosing panencephalitis (SSPE)** is a rare, fatal, late complication of measles, occurring years after the initial infection [1]. - It is a **neurodegenerative disorder** but does not account for the majority of acute measles-related deaths. *Myocarditis* - **Myocarditis**, or inflammation of the heart muscle, is a rare but severe complication of measles. - Although it can be fatal, it is not as common a cause of death as respiratory complications.

Question 1222: What is the minimum induration measurement for a positive Tuberculin test?

A. >5mm
B. >7mm
C. >10mm (Correct Answer)
D. >2mm

Explanation: >10mm - A positive tuberculin skin test (TST) with an induration of **>10mm** is generally considered significant in the general population with no known risk factors for TB. - This cutoff helps identify individuals who have been infected with **Mycobacterium tuberculosis** and have developed a delayed-type hypersensitivity response. *>2mm* - An induration of **>2mm** is too small to be considered a positive TST result in any risk group. - Such a small reaction is typically interpreted as **negative** or non-specific. *>5mm* - An induration of **>5mm** is considered positive in specific high-risk groups, such as individuals with **HIV infection**, recent close contacts of TB cases, or those with **fibrotic changes** on chest X-ray consistent with prior TB. - It is not the general cutoff for a positive test in the broader population. *>7mm* - An induration of **>7mm** does not correspond to a standard interpretive cutoff for a positive TST in any established guideline. - It falls between the **>5mm** (high-risk) and **>10mm** (general population) criteria, making it an incorrect general threshold.

Question 1223: Waterhouse-Friderichsen syndrome is seen in:

A. Neisseria meningitidis (Correct Answer)
B. Yersinia
C. Pseudomonas
D. Pneumococci

Explanation: ***Neisseria meningitidis*** - **Waterhouse-Friderichsen syndrome** is a severe complication of **meningococcal sepsis**, predominantly caused by *Neisseria meningitidis* [1]. - It is characterized by **adrenal gland hemorrhage**, leading to acute adrenal insufficiency, hemorrhagic skin rash, and shock [1]. *Pseudomonas* - While *Pseudomonas aeruginosa* can cause severe infections, including sepsis, it is **not typically associated** with Waterhouse-Friderichsen syndrome. - *Pseudomonas* infections often lead to **ecthyma gangrenosum** in immunocompromised patients, a different dermatological manifestation. *Yersinia* - *Yersinia* species can cause various infections, such as **yersiniosis** (gastroenteritis) and **plague** (*Yersinia pestis*). - These infections do not commonly present with the distinct features of **adrenal hemorrhage** and **fulminant sepsis** seen in Waterhouse-Friderichsen syndrome. *Pneumococci* - *Streptococcus pneumoniae* (**pneumococci**) is a common cause of **meningitis** and **sepsis**, especially in children and the elderly. - Although it can lead to severe bloodstream infections, it is **rarely specifically linked** to the adrenal hemorrhage syndrome known as Waterhouse-Friderichsen syndrome.

Question 1224: Most common site for hydatid cyst

A. Lung
B. Liver (Correct Answer)
C. Brain
D. Kidney

Explanation: ***Liver*** - The **liver** is the most common site for hydatid cysts, accounting for approximately **60-70%** of cases [1]. - It often leads to **biliary obstruction** and liver dysfunction, highlighting its impact on the organ. *Kidney* - Hydatid cysts in the **kidney** are rare and account for a small percentage of cases (around **2-5%**). - Symptoms are often nonspecific, including **flank pain** or hematuria, which are not primary concerns. *Brain* - While the **brain** can be affected, it is not a common site; CNS involvement occurs in only **1-2%** of hydatid disease cases. - Symptoms are related to increased intracranial pressure or focal neurological deficits, not typical for hydatid cysts. *Lung* - The **lung** is another site for hydatid cysts but accounts for about **10-20%** of cases. - Presentation may include **cough** and chest pain, making it less common compared to liver involvement.

Question 1225: Which of the following symptoms is commonly associated with giardiasis?

A. Steatorrhea and flatulence (Correct Answer)
B. All of the options
C. Nausea and vomiting
D. Abdominal pain

Explanation: ***Steatorrhea and flatulence*** - **Giardiasis** is an intestinal infection caused by the parasite *Giardia lamblia*, leading to malabsorption and characteristic symptoms [1]. - The parasite attaches to the intestinal lining, interfering with fat absorption, which results in **steatorrhea** (fatty, foul-smelling stools) and increased gas production causing **flatulence** [1]. *Nausea and vomiting* - While **nausea** can occur in giardiasis, **vomiting** is less common as a primary or dominant symptom. - These symptoms are more characteristic of other gastrointestinal infections like **viral gastroenteritis**. *Abdominal pain* - **Abdominal pain** is a general symptom that can occur with many gastrointestinal issues, including giardiasis [1]. - However, it's not as specific or as clinically defining for giardiasis as **steatorrhea** and **flatulence**, which are direct consequences of the parasite's impact on fat absorption. *All of the options* - Although some patients with giardiasis may experience nausea and abdominal pain, **steatorrhea** and **flatulence** are the most direct and specific indicators of the malabsorption caused by *Giardia lamblia* [1]. - Choosing "all of the above" would imply that all listed symptoms are equally common and specific, which is not the case for giardiasis.

Question 1226: Most important feature to diagnose severe pneumonia?

A. Nasal flaring
B. Fast breathing
C. Cyanosis
D. Chest indrawing (Correct Answer)

Explanation: ***Chest indrawing*** - **Chest indrawing** is a critical sign of severe respiratory distress in pneumonia, indicating increased effort needed for breathing as the body attempts to draw in more air. - This symptom suggests that the affected individual's respiratory muscles are working harder than normal to overcome airway obstruction or reduced lung compliance, often leading to **hypoxia**. *Cyanosis* - While a serious sign of **hypoxemia**, **cyanosis** is often a late manifestation and not visible until oxygen saturation drops significantly. - It indicates advanced **respiratory failure** and may not be the earliest or most sensitive indicator of severe pneumonia. *Nasal flaring* - **Nasal flaring** is a sign of increased respiratory effort seen more commonly in infants and young children. - While it indicates **respiratory distress**, it is less specific for the severity of pneumonia compared to chest indrawing, which suggests more pronounced ventilatory compromise. *Fast breathing* - **Fast breathing** (tachypnea) is a common sign of pneumonia across all severities, as the body tries to compensate for reduced oxygen exchange. - However, it is not specific enough on its own to diagnose **severe pneumonia**, and other signs of increased respiratory effort like chest indrawing are needed to indicate severe disease [1].

Question 1227: Most common cause of death in diphtheria is due to

A. Airway obstruction
B. Septic shock
C. Toxic cardiomyopathy (Correct Answer)
D. Descending polyneuropathy (rare)

Explanation: ***Toxic cardiomyopathy*** - Diphtheria toxin primarily targets and damages the **myocardium**, leading to heart failure, arrhythmias, and ultimately death. - Myocardial damage can occur even in mild cases and is the most frequent cause of **fatality** in both treated and untreated diphtheria. *Airway obstruction* - While significant **pharyngeal and laryngeal pseudomembrane formation** can cause severe respiratory distress and obstruction, it is not the most common cause of death overall. - Prompt medical intervention, such as **tracheostomy** or antitoxin administration, can often alleviate acute airway issues. *Septic shock* - Diphtheria itself is a **toxin-mediated disease**, not typically characterized by overwhelming bacterial sepsis leading to septic shock as the primary cause of death. - While secondary infections can occur, direct **toxin-induced organ damage** is the main concern. *Descending polyneuropathy (rare)* - **Neurological complications**, such as polyneuropathy, can occur later in the course of diphtheria due to toxin effects. - However, these are generally less common and less immediately life-threatening than **cardiac complications**, and rarely the direct cause of death.

Question 1228: Which of the following characteristics can be used to differentiate the rash of chickenpox from the rash of smallpox?

A. Deep-seated
B. Pleomorphic (Correct Answer)
C. Centrifugal
D. Multilocular

Explanation: ***Pleomorphic*** - The rash of **chickenpox** is **pleomorphic**, meaning lesions at various stages of development (macules, papules, vesicles, scabs) are present simultaneously in the same body area. - In contrast, a **smallpox** rash is **monomorphic**, with all lesions in a given area appearing at the same stage of development. *Centrifugal* - A **centrifugal distribution** (lesions more concentrated on the face and extremities) is characteristic of **smallpox**. - **Chickenpox** typically has a **centripetal distribution**, with lesions more concentrated on the trunk. *Deep-seated* - **Smallpox** lesions are described as **deep-seated** and feel like "shot under the skin," often associated with significant scarring. - **Chickenpox** lesions are superficial and less likely to cause scarring unless secondarily infected. *Multilocular* - **Smallpox** vesicles and pustules are typically **multilocular**, meaning they have internal septations and do not collapse when punctured. - **Chickenpox** vesicles are unilocular, appearing as a single compartment, and collapse when punctured.

Question 1229: Which of the following conditions does not present with a rash?

A. Scrub typhus
B. Epidemic typhus
C. Endemic typhus
D. Q fever (Correct Answer)

Explanation: ***Q fever*** - **Q fever** is typically characterized by **fever, headache, chills, and myalgia,** but a skin rash is generally absent. - The disease is caused by *Coxiella burnetii* and can lead to pneumonia or hepatitis, without cutaneous manifestations. *Scrub typhus* - **Scrub typhus** characteristically presents with a **maculopapular rash** that may become generalized [1]. - A distinguishing feature is the presence of an **eschar** at the site of the chigger bite [1]. *Epidemic typhus* - **Epidemic typhus** often involves a **macular or maculopapular rash** that begins on the trunk and spreads peripherally, typically sparing the face, palms, and soles [1]. - This rash usually appears 4-7 days after the onset of fever [1]. *Endemic typhus* - **Endemic (murine) typhus** is also associated with a **maculopapular rash**, which tends to be less extensive and less prominent than that seen in epidemic typhus [1]. - The rash typically starts on the trunk and spreads, usually after 4-5 days of fever [1].

Question 1230: Pseudomembranous colitis, all are true except:

A. Blood in stools is a common feature (Correct Answer)
B. Toxin A is responsible for clinical manifestation
C. Summit lesions are early histopathological findings
D. Toxin B is responsible for clinical manifestation

Explanation: ***Blood in stools is a common feature*** - While diarrhea is a hallmark of **pseudomembranous colitis**, **bloody stools** are uncommon and, if present, suggest severe disease or an alternative diagnosis [1]. - The typical presentation involves **watery diarrhea**, abdominal cramps, and fever, not usually overt bleeding [1]. *Toxin A is responsible for clinical manifestation* - **Toxin A (TcdA)** is one of the primary exotoxins produced by *Clostridioides difficile* and contributes significantly to the **inflammation** and fluid secretion seen in pseudomembranous colitis. - It acts as an **enterotoxin**, causing fluid secretion and mucosal damage in the colon [1]. *Summit lesions are early histopathological findings* - **Summit lesions**, also known as "summit pseudomembranes" or **"volcano lesions"**, refer to characteristic histological findings where inflammatory exudates effuse from the tips of damaged crypts. - These are typical early findings in pseudomembranous colitis, demonstrating the focal nature of the **mucosal injury**. *Toxin B is responsible for clinical manifestation* - **Toxin B (TcdB)** is another key exotoxin produced by *Clostridioides difficile*, and it is considered even more **cytotoxic** than Toxin A [1]. - It causes significant **cell damage** and **apoptosis**, playing a crucial role in the development of the pseudomembranes and clinical symptoms [1].

Practice by Chapter

Principles of Antimicrobial Therapy

Practice Questions

Fever of Unknown Origin

Practice Questions

HIV/AIDS and Related Infections

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Tuberculosis and Mycobacterial Diseases

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Tropical and Parasitic Infections

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Viral Infections (Hepatitis, Herpes, etc.)

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Healthcare-Associated Infections

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Fungal Infections

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Sepsis and Septic Shock

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Infection in Immunocompromised Hosts

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Emerging and Re-emerging Infections

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Antimicrobial Resistance

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Vaccination Principles

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