Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 441: Pertussis most severely affects which age group?

A. 2–3
B. 5–7
C. > 10 years
D. <5 (Correct Answer)

Explanation: **<5** - Pertussis, or **whooping cough**, is most severe and common in **infants and young children** who have not yet completed their primary vaccination series. - Children under **five years of age** are particularly vulnerable to severe complications such as pneumonia, seizures, and encephalopathy. *2–3* - While children in this age group can certainly contract pertussis, the peak incidence and severity are generally observed in **younger infants**. - This option is too restrictive as it excludes infants under 2 years who are at high risk. *5–7* - At this age, most children would have received their primary series of pertussis vaccinations, making severe infection **less common**. - Though breakthrough infections can occur, the age group under 5 years is still at higher risk for severe outcomes. *> 10 years* - Adults and older children can get pertussis, but their symptoms are often **milder** and less typical than in infants. - The question asks which age group pertussis affects, implying where it causes the most significant disease, which is not typically in those over 10 years.

Question 442: True about Measles rash appearance:

A. Along with Koplik spots
B. Post measles stage
C. 1-2 days before Koplik spots
D. 1-2 days after Koplik spots (Correct Answer)

Explanation: ***1-2 days after Koplik spots*** - The characteristic **maculopapular rash** of measles typically appears on the **face and behind the ears** about 1-2 days after the onset of Koplik spots. - The rash then spreads **cephalocaudally** (from head to toe) over the next few days. *Along with Koplik spots* - **Koplik spots** are *pathognomonic* for measles and appear on the **buccal mucosa** *before* the rash. - They represent an enanthem, while the rash is an **exanthem**, and they do not appear simultaneously. *Post measles stage* - The post-measles stage is characterized by the fading of the rash, which desquamates, and the patient's recovery. - The rash is a defining feature of the active measles infection and does not appear in the post-measles stage. *1-2 days before Koplik spots* - Koplik spots are among the earliest clinical signs of measles, appearing 1-2 days *before* the skin rash. - The rash does not precede the Koplik spots; rather, it follows their appearance.

Question 443: Most common lesion in fetal toxoplasmosis is -

A. Encephalitis
B. Chorioretinitis (Correct Answer)
C. GI involvement
D. Pulmonary involvement

Explanation: **Chorioretinitis** - **Chorioretinitis** is the most common and classic ocular manifestation of congenital toxoplasmosis, leading to vision impairment and potential blindness. - The parasite (Toxoplasma gondii) has a predilection for retinal tissue, causing inflammation and scarring. *Encephalitis* - While **encephalitis** (inflammation of the brain) can occur in congenital toxoplasmosis, particularly with intracranial calcifications, it is not the single most common lesion compared to chorioretinitis. - Neurological manifestations are significant but often accompany or are less frequent than ocular involvement. *GI involvement* - **Gastrointestinal involvement** is rare in congenital toxoplasmosis and is not considered a common lesion. - The primary targets of the parasite in congenital infection are the central nervous system and the eyes. *Pulmonary involvement* - **Pulmonary involvement** is also uncommon in congenital toxoplasmosis and is not a typical manifestation. - Severe cases of disseminated toxoplasmosis, particularly in immunocompromised individuals, might show lung involvement, but this is not the most common lesion in fetal infection.

Question 444: A child with a fever of 102°F and vesicles in the oral cavity is probably suffering from:

A. Herpes simplex type-I
B. Neutropenia
C. Juvenile periodontitis
D. Acute herpetic gingivostomatitis (Correct Answer)

Explanation: ***Acute herpetic gingivostomatitis*** - This condition is caused by **Herpes simplex virus (HSV-1)** and typically presents in young children with a **high fever**, malaise, and characteristic **vesicular lesions** in the oral cavity that quickly rupture to form painful ulcers. - The combination of **fever** and widespread **oral vesicles** strongly indicates acute herpetic gingivostomatitis. *Herpes simplex type-I* - While HSV-1 is the **etiologic agent** for acute herpetic gingivostomatitis, simply stating "Herpes simplex type-I" as the diagnosis is less specific than the clinical presentation. - HSV-1 can cause various oral conditions, but the described symptoms are best captured by the more specific diagnosis of **acute herpetic gingivostomatitis**. *Neutropenia* - **Neutropenia** is a reduction in neutrophils, which can lead to increased susceptibility to infections and oral ulcers, but it does not directly cause the characteristic **vesicular lesions** described. - The primary presentation would be recurrent severe infections, not necessarily acute fever with widespread oral vesicles. *Juvenile periodontitis* - **Juvenile periodontitis** (now often termed aggressive periodontitis) is a localized form of periodontal disease characterized by rapid **attachment loss** and **bone destruction** around permanent teeth in otherwise healthy adolescents. - It does not present with acute fever and vesicular lesions in the oral cavity.

Question 445: Which vaccine is contraindicated in a child with an uncontrolled progressive neurological disorder?

A. Typhoid
B. Measles
C. DPT (Correct Answer)
D. BCG

Explanation: ***DPT*** - The **pertussis component** of the DPT vaccine has a **contraindication** in children with **progressive or uncontrolled neurological disorders**, including **uncontrolled epilepsy** or **progressive encephalopathy**. - This is because any subsequent neurological event might be incorrectly attributed to the vaccine, and the risk-benefit ratio is unfavorable in unstable neurological conditions. - **Important distinction**: A history of **resolved febrile seizures** or **well-controlled epilepsy** is **NOT a contraindication** for pertussis-containing vaccines as per current IAP and WHO guidelines. - In cases of **progressive neurological disorders**, DPT is deferred until the condition stabilizes. *Typhoid* - **Typhoid vaccines** (both live attenuated Ty21a and inactivated Vi polysaccharide) have no neurological contraindications. - Primary contraindications relate to **immunosuppression** (for live vaccine) or **severe allergic reactions** to previous doses. *Measles* - The **measles vaccine (MMR)** is **not contraindicated** in children with neurological disorders or seizure history. - Even children with **uncontrolled epilepsy** can receive MMR vaccine, as the risk from **natural measles infection** (which causes encephalitis in 1:1000 cases) far exceeds any theoretical vaccine risk. - Post-vaccination fever and febrile seizures can occur but are much less common and severe than complications from measles disease. *BCG* - The **BCG vaccine** has **no neurological contraindications** whatsoever. - Main contraindications are **immunodeficiency states**, **active tuberculosis**, and **generalized septic skin conditions**.

Question 446: All of the following are true about erythema infectiosum EXCEPT?

A. Caused by parvovirus
B. Known as 'fifth disease'
C. Rash initially appears on trunk (Correct Answer)
D. Slapped cheek appearance seen

Explanation: ***Rash initially appears on trunk*** - Erythema infectiosum (fifth disease) characteristically begins with a **'slapped cheek' rash** on the face. - The rash then spreads to the trunk and extremities, taking on a **lacy, reticulated appearance**, but it does not initially appear on the trunk. *Caused by parvovirus* - Erythema infectiosum is caused by **Parvovirus B19**, which primarily infects erythroid progenitor cells. - This virus is highly contagious and spreads via respiratory secretions. *Known as 'fifth disease'* - Erythema infectiosum is one of the classic childhood exanthems and is historically known as **'fifth disease'**. - The numbering sequence refers to the order in which these common childhood rashes were identified. *Slapped cheek appearance seen* - A prominent feature of erythema infectiosum is the classic bright red rash on the cheeks, giving the child a distinctive **'slapped cheek' appearance**. - This facial rash often precedes the lacy rash on the body.

Question 447: The etiological agent for roseola infantum is:

A. Epstein-Barr Virus (EBV)
B. Cytomegalovirus (CMV)
C. Human Herpesvirus 6 (HHV-6) (Correct Answer)
D. Adenovirus

Explanation: ***Human Herpesvirus 6 (HHV-6)*** - **HHV-6** is the primary cause of **roseola infantum**, also known as exanthem subitum. - This virus is responsible for the characteristic high fever followed by a rash often seen in infants and young children. *Epstein-Barr Virus (EBV)* - **EBV** is the causative agent of **infectious mononucleosis**, not roseola infantum. - While both are herpesviruses, their clinical presentations and target cell specificities differ significantly. *Cytomegalovirus (CMV)* - **CMV** is another herpesvirus that can cause a variety of symptoms, especially in immunocompromised individuals or congenitally. - It is not typically associated with the classic presentation of **roseola infantum**. *Adenovirus* - **Adenoviruses** are a common cause of respiratory infections, conjunctivitis, and gastroenteritis. - They do not cause **roseola infantum**, which is characterized by a specific fever-rash sequence.

Question 448: In early congenital syphilis, which is not seen?

A. Keratitis (Correct Answer)
B. Vesicular rash
C. Chorioretinitis
D. Rhinitis

Explanation: ***Keratitis*** - **Keratitis** (inflammation of the cornea) is a manifestation of **late congenital syphilis**, typically appearing in children older than 2 years. - It is often associated with other features of **Hutchinson's triad**, which includes **Hutchinson's teeth** and **sensorineural hearing loss**. *Vesicular rash* - A **maculopapular rash**, which can sometimes be vesicular or bullous, is a common finding in **early congenital syphilis**, particularly on the palms and soles. - This rash is a sign of active infection and can be highly infectious due to the presence of **spirochetes**. *Chorioretinitis* - **Chorioretinitis** (inflammation of the choroid and retina) is an important ocular manifestation of **early congenital syphilis**. - It can lead to significant vision impairment if not promptly diagnosed and treated. *Rhinitis* - Known as **"snuffles,"** rhinitis is a classic and common symptom of **early congenital syphilis**, often presenting with mucopurulent or hemorrhagic nasal discharge. - The nasal discharge contains infectious **Treponema pallidum** and can cause significant respiratory distress in infants.

Question 449: Most common bacterial cause of pneumonia in children is?

A. Streptococcus pneumoniae (Correct Answer)
B. Staphylococcus aureus
C. RSV
D. Klebsiella

Explanation: ***Streptococcus pneumoniae*** - **_Streptococcus pneumoniae_** is the most frequent **bacterial** cause of pneumonia across all pediatric age groups, leading to **lobar pneumonia** - It accounts for the majority of bacterial pneumonia cases requiring hospitalization in children - **Vaccination** (PCV13/PCV15) has significantly reduced its incidence but it remains the leading bacterial pathogen *Staphylococcus aureus* - **_Staphylococcus aureus_** is a less common bacterial cause in children unless there are predisposing factors like **recent influenza infection**, **cystic fibrosis**, or **immunocompromised states** - When it occurs, it often presents with more severe features including **necrotizing pneumonia**, **empyema**, and **abscess formation** *RSV* - **Respiratory Syncytial Virus (RSV)** is the most common **viral** cause of lower respiratory tract infections in infants and young children, particularly **bronchiolitis** and viral pneumonia - While RSV causes more overall pneumonia cases in young children, the question asks specifically for **bacterial** causes *Klebsiella* - **_Klebsiella pneumoniae_** is an **uncommon cause** of pneumonia in otherwise healthy children - It typically affects individuals with **compromised immune systems**, **chronic lung disease**, or occurs as a **nosocomial infection**

Question 450: Which of the following is the most common late toxic manifestation of diphtheria in a child?

A. Polyneuritis (Correct Answer)
B. Renal failure
C. Myocarditis
D. Septicemia

Explanation: ***Polyneuritis*** - **Polyneuritis** is the **most common late toxic manifestation** of diphtheria, typically appearing **2-6 weeks or more** after the onset of infection. - It results from the **diphtheria toxin's neurotoxic effects**, causing demyelination of peripheral nerves. - Clinical features include **cranial nerve palsies** (especially palatal and pharyngeal weakness), **limb weakness**, and **areflexia**. - It can persist for weeks to months and is the characteristic delayed complication. *Renal failure* - While diphtheria toxin can cause **acute tubular necrosis**, renal failure is **uncommon** and not a primary late toxic manifestation. - When kidney injury occurs, it is typically mild and occurs earlier in the acute phase rather than as a delayed complication. *Myocarditis* - **Myocarditis** is a serious complication of diphtheria occurring in **10-25% of cases**, typically appearing in **weeks 2-6**. - While it overlaps with the timing of late manifestations, it generally presents **earlier in that window** (often weeks 2-3) compared to polyneuritis. - It is a **major cause of mortality** in diphtheria, but **polyneuritis is more common as a late manifestation** presenting after week 3-4. - Clinical features include arrhythmias, heart failure, and conduction defects. *Septicemia* - **Septicemia** is not a direct toxic manifestation of *Corynebacterium diphtheriae*. - Diphtheria causes disease primarily through **localized infection and systemic toxin effects**, not through bloodstream invasion. - Secondary bacterial superinfection is possible but is not a characteristic manifestation of diphtheria toxicity.

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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