Infectious Diseases Practice Questions

Q: Which of the following statements about polio is false?

Increased tendon reflexes. ***Increased tendon reflexes*** - Polio causes **lower motor neuron damage**, specifically to the anterior horn cells of the spinal cord [1]. - This damage leads to **flaccid paralysis** and **decreased or absent deep tendon reflexes**, not increased reflexes [3]. *99% non paralytic* - The vast majority of poliovirus infections (approximately 95-99%) are **asymptomatic** or cause only mild, non-specific symptoms. - Only a small percentage of infected individuals develop the more severe paralytic form of the disease. *Flaccid paralysis* - Poliovirus directly attacks and destroys **motor neurons** in the anterior horn of the spinal cord [1]. - This damage results in **muscle weakness** and loss of muscle tone, leading to **flaccid paralysis** [3]. *Aseptic meningitis* - About 1-5% of poliovirus infections can manifest as **aseptic meningitis**, characterized by symptoms like fever, headache, neck stiffness, and vomiting without bacterial infection [2]. - This form of meningitis is typically **self-limiting** and does not lead to paralysis [2].

Q: Which of the following conditions is least commonly associated with Pneumocystis carinii in AIDS?

Otic polypoid mass. ***Otic polypoid mass*** - While *Pneumocystis jirovecii* (formerly *carinii*) can cause **extrapulmonary disease** in immunocompromised patients, an **otic polypoid mass** is an extremely rare and atypical presentation. - Extrapulmonary manifestations usually involve organs with rich vascular supply, but ear involvement in this form is not a characteristic feature. *Pneumonia* - **Pneumocystis pneumonia (PCP)** is the **most common opportunistic infection** and AIDS-defining illness caused by *Pneumocystis jirovecii* in individuals with AIDS [1]. - It typically manifests as **fever, cough, and dyspnea** with characteristic imaging findings [1]. *Ophthalmic choroid lesion* - **Choroid lesions** due to *Pneumocystis jirovecii* are a recognized, albeit less common, **extrapulmonary manifestation** in immunocompromised patients, particularly those with AIDS. - These lesions are usually **asymptomatic** and discovered incidentally on funduscopic examination. *Meningitis* - Although *Pneumocystis jirovecii* causing **meningitis** is rare, it has been reported in severely immunocompromised individuals with AIDS, often as part of disseminated disease. - Central nervous system involvement signifies **widespread dissemination** and advanced immunosuppression.

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

Pleomorphic. ***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.

Q: Which of the following is true about Hepatitis A virus?

Common cause of hepatitis in children. ***Common cause of hepatitis in children*** - **Hepatitis A virus (HAV)** infection is often acquired in childhood, particularly in areas with poor sanitation, and many infections are **asymptomatic** or mild in children [1]. - Due to their developing immune systems and often exposure in daycare or school settings, children are a highly susceptible population for HAV transmission [1]. *Causes cirrhosis* - **HAV infection** is an **acute self-limiting illness** and typically does not lead to chronic liver disease or cirrhosis [1]. - **Cirrhosis** is primarily associated with chronic viral hepatitis (e.g., HBV, HCV), alcohol-related liver disease, or certain autoimmune conditions. *Helps HDV replication* - **Hepatitis D virus (HDV)** is a **defective virus** that requires the presence of **Hepatitis B virus (HBV)** surface antigen (HBsAg) for its replication and assembly [1]. - **HAV** has no role in the replication or pathogenesis of **HDV** [1]. *Causes chronic hepatitis* - **HAV infection** results in an **acute inflammatory response** in the liver that resolves spontaneously in most cases [1]. - Unlike **HBV** and **HCV**, **HAV** does not establish a persistent infection and, therefore, does not cause chronic hepatitis [1].

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

Respiratory tract infections (RTIs). ***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.

Q: Most common cause of death in diphtheria is due to

Toxic cardiomyopathy. ***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.

Q: Most common site for hydatid cyst

Liver. ***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.

Q: Pseudomembranous colitis, all are true except:

Blood in stools is a common feature. ***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].

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

Steatorrhea and flatulence. ***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.

Q: Waterhouse-Friderichsen syndrome is seen in:

Neisseria meningitidis. ***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 1

Which of the following statements about polio is false?

Accepted Answer

Increased tendon reflexes

Answer

99% non paralytic

Answer

Aseptic meningitis

Answer

Flaccid paralysis

Question 2

Which of the following conditions is least commonly associated with Pneumocystis carinii in AIDS?

Accepted Answer

Otic polypoid mass

Answer

Meningitis

Answer

Pneumonia

Answer

Ophthalmic choroid lesion

Question 3

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

Accepted Answer

Pleomorphic

Answer

Deep-seated

Answer

Centrifugal

Answer

Multilocular

Question 4

Which of the following is true about Hepatitis A virus?

Accepted Answer

Common cause of hepatitis in children

Answer

Causes chronic hepatitis

Answer

Helps HDV replication

Answer

Causes cirrhosis

Question 5

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

Accepted Answer

Respiratory tract infections (RTIs)

Answer

Diarrhea

Answer

SSPE

Answer

Myocarditis

Question 6

Most common cause of death in diphtheria is due to

Accepted Answer

Toxic cardiomyopathy

Answer

Airway obstruction

Answer

Septic shock

Answer

Descending polyneuropathy (rare)

Question 7

Most common site for hydatid cyst

Accepted Answer

Liver

Answer

Lung

Answer

Brain

Answer

Kidney

Question 8

Pseudomembranous colitis, all are true except:

Accepted Answer

Blood in stools is a common feature

Answer

Toxin A is responsible for clinical manifestation

Answer

Summit lesions are early histopathological findings

Answer

Toxin B is responsible for clinical manifestation

Question 9

Which of the following symptoms is commonly associated with giardiasis?

Accepted Answer

Steatorrhea and flatulence

Answer

All of the options

Answer

Nausea and vomiting

Answer

Abdominal pain

Question 10

Waterhouse-Friderichsen syndrome is seen in:

Accepted Answer

Neisseria meningitidis

Answer

Yersinia

Answer

Pseudomonas

Answer

Pneumococci

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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