Infectious Diseases — MCQs

An 11-year-old child with a history of streptococcal pharyngitis presents you with fever and arthralgia. There is no past history of rheumatic heart disease or features of carditis or valvular disease. How often is 600,000 IU of benzathine penicillin recommended for prophylaxis of rheumatic heart disease?

Q548

All are true about congenital Toxoplasmosis EXCEPT which of the following?

Q549

A child with a family history of allergies presents with pruritus on the face and convexities, followed by the development of numerous umbilicated vesicles that become pustular, hemorrhagic, and crusted. After two days, the child develops a high fever and lymphadenopathy. What is the most likely diagnosis?

Q550

At what age group is Streptococcus pneumoniae pneumonia most commonly observed?

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 541: What virus is primarily responsible for causing Exanthema subitum?

A. HHV-6 (Correct Answer)
B. HHV-8
C. Parvovirus
D. Coxsackievirus

Explanation: ***HHV-6*** - **Human Herpesvirus 6 (HHV-6)** is the primary causative agent of **Exanthema subitum**, also known as **Roseola infantum**. - This virus typically infects infants and young children, leading to a high fever followed by a characteristic rash. *HHV-8* - **Human Herpesvirus 8 (HHV-8)** is primarily associated with **Kaposi's sarcoma**, a cancer that affects individuals with weakened immune systems. - It is not implicated in Exanthema subitum. *Parvovirus* - **Parvovirus B19** causes **Fifth disease** (Erythema infectiosum), characterized by a "slapped cheek" rash. - Its clinical presentation, including the rash distribution and timing relative to fever, differs from Exanthema subitum. *Coxsackievirus* - **Coxsackievirus** is responsible for **Hand-foot-and-mouth disease** and herpangina, which involve rashes and lesions primarily on the hands, feet, and mouth or throat. - Exanthema subitum does not typically present with these specific dermatological features.

Question 542: A 5-year-old child presents with a honey-colored crusted lesion on their face. What is the most likely causative organism?

A. Staphylococcus aureus
B. Streptococcus pyogenes (Correct Answer)
C. Candida albicans
D. Pseudomonas aeruginosa

Explanation: ***Streptococcus pyogenes*** - *Streptococcus pyogenes* (Group A Streptococcus) is the **most common causative organism** of **non-bullous impetigo**, which characteristically presents with **honey-colored crusted lesions**. - Non-bullous impetigo accounts for **70% of all impetigo cases** and typically affects the face, particularly around the mouth and nose. - The honey-colored crusts form when the serous exudate from ruptured vesicles dries on the skin surface. - **Important complication:** Post-streptococcal glomerulonephritis can occur 1-3 weeks after skin infection. *Staphylococcus aureus* - *S. aureus* is the primary cause of **bullous impetigo** (30% of cases), which presents with **fluid-filled bullae** rather than honey-colored crusts. - While *S. aureus* can co-infect with *S. pyogenes* in non-bullous impetigo, it is **not the primary pathogen** in the classic honey-crusted presentation described. - *S. aureus* produces exfoliative toxins that cause bullae formation in bullous impetigo. *Pseudomonas aeruginosa* - *Pseudomonas aeruginosa* is typically associated with **hot tub folliculitis**, infections in immunocompromised individuals, or puncture wounds. - Infections characteristically produce **bluish-green pus** with a fruity odor, not honey-colored crusts. - Not a typical cause of impetigo in healthy children. *Candida albicans* - *Candida albicans* causes **fungal infections** such as oral thrush, diaper dermatitis, or intertrigo in skin folds. - Presents with **erythematous patches with satellite lesions**, not honey-colored crusts. - The lesions are typically moist, macerated, and pruritic rather than crusted.

Question 543: An infant presents with hepatosplenomegaly and thrombocytopenia. Neuroimaging with CT shows periventricular calcifications. What is the most likely diagnosis?

A. Congenital rubella syndrome
B. Congenital herpes simplex virus infection
C. Congenital toxoplasmosis
D. Congenital cytomegalovirus infection (Correct Answer)

Explanation: ***Congenital cytomegalovirus infection*** - **Periventricular calcifications** on neuroimaging are a classic and highly suggestive finding for congenital CMV infection. - **Hepatosplenomegaly** and **thrombocytopenia** are common systemic manifestations of congenital CMV, which can be severe. *Congenital rubella syndrome* - Rubella typically causes **sensorineural hearing loss**, ocular abnormalities (e.g., cataracts), and congenital heart defects (e.g., patent ductus arteriosus), rather than periventricular calcifications. - While hepatosplenomegaly and thrombocytopenia can occur, the specific brain calcification pattern points away from rubella. *Congenital herpes simplex virus infection* - HSV infection in neonates presents with a variety of symptoms, including skin vesicles, keratoconjunctivitis, and seizures. - Brain imaging often shows **focal necrosis** or **encephalitis**, not typically periventricular calcifications unless it's a very widespread and destructive process. *Congenital toxoplasmosis* - Congenital toxoplasmosis classic triad includes **chorioretinitis**, **hydrocephalus**, and **intracranial calcifications**, but these calcifications are typically scattered or diffuse rather than strictly periventricular. - While hepatosplenomegaly and thrombocytopenia can be present, the specific location of calcifications is a key differentiating factor.

Question 544: A child presents with a fever and a rash. Urine examination showed cells with owl's eye appearance. What is the most likely diagnosis?

A. Herpes simplex virus infection
B. Toxoplasmosis caused by Toxoplasma gondii
C. Cytomegalovirus (CMV) infection (Correct Answer)
D. Infectious mononucleosis caused by Epstein-Barr virus

Explanation: ***Cytomegalovirus (CMV) infection*** - The presence of cells with an **owl's eye appearance** in urine sediment is a classic histological hallmark of **CMV infection**. - CMV can cause a variety of symptoms in children, including **fever and rash**, making this the most likely diagnosis. *Herpes simplex virus infection* - HSV causes characteristic **vesicular lesions** on mucocutaneous surfaces, often associated with fever. - While HSV can cause systemic illness, it does not typically present with **owl's eye inclusions** in urine cells. *Toxoplasmosis caused by Toxoplasma gondii* - **Toxoplasmosis** can cause fever and rash, especially in congenital infections or immunocompromised individuals. - However, it does not lead to **owl's eye inclusions** in urinary cells, which are pathognomonic for CMV. *Infectious mononucleosis caused by Epstein-Barr virus* - **Infectious mononucleosis** commonly presents with fever, fatigue, and lymphadenopathy, sometimes with a rash. - **Epstein-Barr virus (EBV)** infection does not produce cells with an **owl's eye appearance** in the urine; that is specific to CMV.

Question 545: A 3-month-old baby presents with deafness, cataract, and patent ductus arteriosus. Which of the following is the most likely diagnosis?

A. Congenital herpes simplex virus infection
B. Congenital toxoplasmosis
C. Congenital cytomegalovirus infection
D. Congenital rubella syndrome (Correct Answer)

Explanation: ***Congenital rubella syndrome*** - The classic triad of **deafness**, **cataracts**, and **patent ductus arteriosus (PDA)** is highly characteristic of congenital rubella syndrome. - This syndrome results from **maternal rubella infection** during the first trimester of pregnancy. *Congenital herpes simplex virus infection* - Typically presents with **skin vesicles**, **keratoconjunctivitis**, and **encephalitis**. - **Deafness, cataracts, and PDA** are not common features of congenital HSV. *Congenital toxoplasmosis* - The classic triad involves **chorioretinitis**, **hydrocephalus**, and **intracranial calcifications**. - While it can cause microcephaly and seizures, **deafness, cataracts, and PDA** are not hallmark features. *Congenital cytomegalovirus infection* - Often causes **sensorineural hearing loss** and sometimes **chorioretinitis**, but the combination with **cataracts** and **PDA** is atypical. - Other common features include **periventricular calcifications**, **hepatosplenomegaly**, and **thrombocytopenia**.

Question 546: What is the most serious complication of measles?

A. Croup
B. Otitis media
C. Meningo-encephalitis
D. Pneumonia (Correct Answer)

Explanation: ***Pneumonia*** - **Pneumonia**, particularly **giant cell pneumonia**, is the most common cause of **measles-related deaths** in young children. - It results from the **direct viral infection** of the lungs or a **secondary bacterial superinfection**. *Croup* - **Croup (laryngotracheobronchitis)** can be a complication of measles, but it is typically **less severe** and **less life-threatening** than pneumonia. - It primarily affects the **upper airways**, causing a barking cough and stridor. *Meningo-encephalitis* - **Meningo-encephalitis** is a serious, albeit **less common**, complication of measles, occurring in approximately 1 in 1,000 cases. - While potentially fatal or leading to neurological sequelae, it is **outranked by pneumonia** in terms of overall mortality attributed to measles. *Otitis media* - **Otitis media** (middle ear infection) is a common complication of measles, but it is generally **not life-threatening**. - It usually responds well to **antibiotic treatment** and rarely leads to severe outcomes.

Question 547: An 11-year-old child with a history of streptococcal pharyngitis presents you with fever and arthralgia. There is no past history of rheumatic heart disease or features of carditis or valvular disease. How often is 600,000 IU of benzathine penicillin recommended for prophylaxis of rheumatic heart disease?

A. Immediately
B. Thrice weekly lifelong
C. Once in three weeks for 10 years or till the age of 25, whichever is longer
D. Once in three weeks for 5 years or till the age of 18, whichever is longer (Correct Answer)

Explanation: ***Once in three weeks for 5 years or till the age of 18, whichever is longer*** - For patients with a history of **rheumatic fever** but **no carditis**, secondary prophylaxis with benzathine penicillin G is recommended for **5 years** or until **age 18**, whichever is longer. - The usual dose of benzathine penicillin G for children (under 27 kg) is **600,000 IU** intramuscularly every 3-4 weeks. *Immediately* - This option refers to the timing of initial treatment for **streptococcal pharyngitis**, not the duration or frequency of secondary prophylaxis. - Initiating antibiotic treatment immediately for acute strep throat prevents **acute rheumatic fever**, but long-term prophylaxis follows guidelines. *Thrice weekly lifelong* - This frequency is incorrect; secondary prophylaxis is typically given every **3-4 weeks**, not three times a week. - Lifelong prophylaxis is generally reserved for patients with severe **rheumatic heart disease** or those undergoing valve replacement, which is not the case here. *Once in three weeks for 10 years or till the age of 25, whichever is longer* - This duration is recommended for patients with **rheumatic fever with carditis but no residual heart disease**. - For patients with **carditis** and **residual heart disease**, prophylaxis is often extended for **10 years** or until **age 40**, or even lifelong in severe cases.

Question 548: All are true about congenital Toxoplasmosis EXCEPT which of the following?

A. Hydrocephalus
B. Cerebral calcification
C. Conjunctivitis (Correct Answer)
D. Chorioretinitis

Explanation: ***Conjunctivitis*** - **Conjunctivitis** is inflammation of the conjunctiva and is not a hallmark symptom of congenital toxoplasmosis. - While it can occur in an infant due to other causes, it is not specifically caused by *Toxoplasma gondii* infection. *Chorioretinitis* - **Chorioretinitis** is a classic ocular manifestation of congenital toxoplasmosis, leading to inflammation and scarring of the retina and choroid. - It can cause significant visual impairment and is a key component of the **classic triad** of symptoms. *Hydrocephalus* - **Hydrocephalus**, an abnormal accumulation of cerebrospinal fluid, is a severe neurological complication of congenital toxoplasmosis. - It results from obstruction of CSF flow due to inflammation or damage caused by the parasite in the brain. *Cerebral calcification* - **Cerebral calcifications** are highly suggestive of congenital toxoplasmosis, representing areas of brain tissue damage and healing where the parasite has been active. - These are typically visible on brain imaging and are a key diagnostic indicator.

Question 549: A child with a family history of allergies presents with pruritus on the face and convexities, followed by the development of numerous umbilicated vesicles that become pustular, hemorrhagic, and crusted. After two days, the child develops a high fever and lymphadenopathy. What is the most likely diagnosis?

A. Secondary infected atopic dermatitis
B. Herpes simplex virus infection (Correct Answer)
C. Molluscum contagiosum
D. Eczema vaccinatum

Explanation: ***Herpes simplex virus infection (Eczema herpeticum)*** - The presentation of **numerous umbilicated vesicles** that become **pustular, hemorrhagic, and crusted** in a child with atopic dermatitis is pathognomonic of **eczema herpeticum** (Kaposi varicelliform eruption). - **High fever** and **lymphadenopathy** developing after two days indicate systemic HSV infection, a characteristic feature of eczema herpeticum. - This is a **dermatological emergency** requiring immediate antiviral therapy (acyclovir) as it can progress to disseminated HSV infection with high morbidity. - The distribution on **face and convexities** matches typical atopic dermatitis sites where HSV superinfection occurs. *Eczema vaccinatum* - While clinically similar to eczema herpeticum, eczema vaccinatum is caused by **vaccinia virus** (smallpox vaccine complication). - This condition is **historically important but extremely rare today** since routine smallpox vaccination was discontinued in the 1970s-1980s. - In modern clinical practice and contemporary medical exams, eczema herpeticum (HSV) is the relevant diagnosis for this presentation. *Secondary infected atopic dermatitis* - Bacterial superinfections (usually *Staphylococcus aureus* or *Streptococcus*) typically produce **honey-colored crusts** (impetigo) or weeping, purulent lesions. - They do **not** produce the characteristic **umbilicated vesicles** described in this case. - The rapid, widespread vesicular eruption with systemic symptoms points to viral rather than bacterial etiology. *Molluscum contagiosum* - Presents as **discrete, pearly, dome-shaped umbilicated papules** that are chronic and typically asymptomatic. - Does **not** cause acute systemic symptoms like high fever and lymphadenopathy. - Does **not** progress to pustular, hemorrhagic, and crusted lesions as described in this case.

Question 550: At what age group is Streptococcus pneumoniae pneumonia most commonly observed?

A. < 5 years (Correct Answer)
B. 5 - 15 years
C. 20 - 25 years
D. 30 - 40 years

Explanation: ***< 5 years*** - *Streptococcus pneumoniae* pneumonia is particularly common and severe in **young children**, especially those under the age of 5, due to their developing immune systems. - This age group has a higher incidence of **invasive pneumococcal disease**, including pneumonia and meningitis, making vaccination crucial. *5 - 15 years* - While pneumonia can occur in this age group, it is **less common** than in very young children or older adults. - The immune system is generally more developed and effective at this age, leading to a **lower incidence** of severe pneumococcal infections. *20 - 25 years* - This age group generally has a robust immune system, making *Streptococcus pneumoniae* pneumonia **uncommon** unless there are underlying risk factors such as immunocompromise or chronic medical conditions. - Most cases of pneumonia in young adults are often due to **viral pathogens** or *Mycoplasma pneumoniae*. *30 - 40 years* - Similar to the 20-25 years age group, incidence of *Streptococcus pneumoniae* pneumonia remains **relatively low** in healthy individuals in their 30s and 40s. - Increased risk is typically associated with **chronic illnesses**, smoking, or conditions that weaken the immune system.

Practice by Chapter

Vaccine-Preventable Diseases

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Immunization Schedule

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Common Childhood Infections

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Pediatric HIV

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Congenital Infections

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Fever in Infants and Children

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Meningitis and Encephalitis

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Respiratory Tract Infections

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Gastrointestinal Infections

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Parasitic Infections

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Tuberculosis in Children

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Opportunistic Infections

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