Infectious Diseases Practice Questions

Q: A child presents with fever, conjunctival redness, and bluish -white spots on the buccal mucosa. What is the most likely diagnosis?

Measles. ***Measles*** - The presence of **Koplik spots** (bluish-white spots on the buccal mucosa) is a pathognomonic feature of **measles** (rubeola) infection. - The clinical triad of **cough, coryza, and conjunctivitis** (the 3 Cs) alongside high fever strongly supports this diagnosis. *Mumps* - Primarily presents with **parotitis** (swelling and tenderness of the parotid glands), not conjunctival redness or specific buccal spots. - It is caused by the **mumps virus**, which typically involves glandular structures like salivary glands, testes, or ovaries. *Chickenpox* - Characterized by a **vesicular rash** that appears in different stages (macules, papules, vesicles, crusts) simultaneously. - The hallmark is a **pruritic rash** that starts centrally and spreads peripherally, distinguishable from the morbilliform rash of measles. *Rubella* - Also known as German measles, it typically features a **fine, pink maculopapular rash** and marked **lymphadenopathy** (especially postauricular and suboccipital). - While it presents with fever, it lacks the classic **Koplik spots** seen in true measles and is generally a milder, shorter-lived illness.

Q: A child presents with fever, altered level of consciousness, and signs of meningeal irritation. Cerebrospinal fluid (CSF) analysis reveals the following findings: - Cell differential: Predominantly lymphocytes - Protein: Elevated - Glucose: Low Based on these CSF findings, what is the most likely diagnosis?

Tuberculous meningitis. ***Tuberculous meningitis*** - The combination of **lymphocytic pleocytosis** with **elevated protein** (often very high) and **low glucose** (hypoglycorrhachia) is a classic CSF profile for tuberculous meningitis. - Patients often present with a subacute course involving **fever**, **altered mental status**, and meningeal signs, which distinguishes it from the more acute bacterial or viral etiologies. *Pyogenic (bacterial) meningitis* - Typically presents with a **neutrophilic pleocytosis** rather than lymphocytic, reflecting a profound acute inflammatory response. - Glucose levels are generally very low, but the cell count is usually significantly higher compared to tuberculosis, showing thousands of cells per microliter. *Viral meningitis* - While this also presents with **lymphocytic pleocytosis**, glucose levels are almost always **normal** because viruses do not consume glucose from the CSF. - Protein levels are typically normal or only mildly elevated, unlike the significant elevation seen in this patient. *Fungal meningitis* - Although it can present with low glucose and high protein, it is generally an **opportunistic infection** found in immunocompromised patients rather than a typical presentation in a standard pediatric case. - While the CSF profile can overlap, clinical context (such as known HIV status or chemotherapy) is usually required to differentiate it from TB; TB remains the most likely cause for this specific triad of CSF findings in most clinical settings.

Q: Which of the following is NOT a recognized diagnostic feature of Kawasaki disease?

Purulent conjunctivitis. ***Purulent conjunctivitis*** - Kawasaki disease is characterized by **bilateral conjunctival injection** that is notably **non-purulent** (non-exudative). - The presence of **purulent discharge** strongly suggests a bacterial cause, making it an exclusionary criterion for the clinical diagnosis of Kawasaki disease. *Non-purulent (bilateral) conjunctivitis* - This is a cardinal clinical criterion, typically appearing early in the course of the illness. - The inflammation involves the **bulbar conjunctiva** without exudate or limbal sparing. *Cervical lymphadenopathy* - This is a recognized diagnostic criterion, usually defined as a node greater than **1.5 cm** in diameter, which is typically unilateral and cervical. - It is often the least frequently observed criterion among the classic features. *Fever lasting more than 5 days* - Persistent, high-grade fever of at least **5 days' duration** is the sine qua non (essential) diagnostic criterion. - Fever in Kawasaki disease is often high and typically unresponsive to standard **antipyretics** and **antibiotics**.

Q: A 6-week-old infant with prolonged NICU stay with presentation of fever, lethargy, poor feeding with CSF analysis showing features of bacterial meningitis. Which of the following are responsible? a. Staphylococcus aureus b. Hemophilus influenzae c. Streptococcus pneumoniae d. Listeria Choose the correct answer:

All of the above. ***All of the above*** - In a **6-week-old infant** who has stayed in the **NICU**, the etiology of meningitis is broad and reflects both community-acquired and hospital-acquired (**nosocomial**) risk factors. - All listed organisms—**Staphylococcus aureus**, **Haemophilus influenzae**, **Streptococcus pneumoniae**, and **Listeria monocytogenes**—are clinically relevant pathogens capable of causing meningitis in this population depending on maternal transmission, colonization, and environmental exposure. *Listeria* - While classically associated with **neonatal early-onset disease** (transplacental transmission), it remains a significant pathogen in this age group due to its ability to persist. - It is a facultative intracellular organism that often requires specific suspicion, especially in infants with compromised immunity or history of NICU admission. *b and d* - This option is incomplete as it ignores **Staphylococcus aureus** and **Streptococcus pneumoniae**, which are common causes of **healthcare-associated meningitis** in NICU environments. - Excluding these common pathogens fails to account for the risk of indwelling lines and procedure-related infections prevalent in NICU stays. *a, b, d* - This option is incorrect because it erroneously omits **Streptococcus pneumoniae**. - **Streptococcus pneumoniae** is a leading cause of bacterial meningitis in infants, and excluding it provides an insufficient assessment of the differential diagnosis.

Q: Sternal edema is seen in which of the following conditions?

Mumps. **Explanation:** **Mumps** is the correct answer. While parotitis is the most common manifestation of Mumps, involvement of the submandibular glands can lead to a specific and high-yield clinical sign: **presternal edema**. This occurs due to lymphatic obstruction caused by the significantly enlarged submandibular salivary glands, which impede the lymphatic drainage from the anterior chest wall. This finding is a classic "spotter" for Mumps in pediatric examinations. **Analysis of Incorrect Options:** * **Measles:** Characterized by the "3 Cs" (Cough, Coryza, Conjunctivitis), Koplik spots, and a maculopapular rash starting behind the ears. It does not involve salivary gland swelling or sternal edema. * **Diphtheria:** Known for the "bull neck" appearance due to massive cervical lymphadenopathy and soft tissue edema, and the presence of a greyish pseudomembrane. While it causes neck swelling, it does not typically present with isolated presternal edema. * **Varicella (Chickenpox):** Presents with a characteristic pleomorphic rash (vesicles on an erythematous base, "dewdrop on a rose petal"). It does not involve the lymphatic obstruction required to produce sternal edema. **NEET-PG High-Yield Pearls for Mumps:** * **Most common complication in children:** Aseptic meningitis. * **Most common complication in post-pubertal males:** Orchitis (usually unilateral; rarely leads to sterility). * **Most common cause of isolated viral pancreatitis** in children. * **Sensorineural Hearing Loss (SNHL):** A rare but serious permanent complication. * **Diagnosis:** Usually clinical; confirmed by elevated serum amylase or IgM antibodies.

Q: What is NOT a common cause of meningitis in an 8-year-old child?

Staphylococcus aureus. In pediatric meningitis, the causative organisms vary significantly based on the child's age. For children aged 2 to 18 years, the most common pathogens are encapsulated bacteria. **Explanation of the Correct Answer:** **C. Staphylococcus aureus:** This is **not** a common cause of community-acquired meningitis in healthy children. *S. aureus* typically causes meningitis only in specific clinical contexts, such as post-neurosurgical procedures, penetrating head trauma, or the presence of an infected CSF shunt (VP shunt). In a standard 8-year-old child without these risk factors, it is an uncommon primary pathogen. **Explanation of Incorrect Options:** * **A. Streptococcus pneumoniae:** This remains the most common cause of bacterial meningitis in children over 2 years of age in the post-vaccine era. It is associated with the highest morbidity and mortality. * **B. Haemophilus influenzae (Type b):** While the incidence has drastically reduced due to the Hib vaccine, it remains a recognized cause of meningitis in unimmunized or under-immunized children. * **D. Neisseria meningitidis:** This is a leading cause of bacterial meningitis in children and adolescents, often occurring in outbreaks or clusters. It is classically associated with a petechial or purpuric rash. **High-Yield Clinical Pearls for NEET-PG:** * **Neonates ( 10 years):** *N. meningitidis* becomes increasingly prevalent. * **CSF Findings:** Bacterial meningitis typically shows low glucose ( 100 mg/dL), and neutrophilic pleocytosis.

Q: Bull's neck is characteristically seen in which of the following conditions?

Diphtheria. **Explanation:** **Diphtheria (Option B)** is the correct answer. The "Bull's neck" appearance is a classic clinical hallmark of **Faucial Diphtheria**, caused by *Corynebacterium diphtheriae*. This appearance results from massive swelling of the cervical lymph nodes (lymphadenopathy) combined with extensive edema of the surrounding soft tissues in the neck. It is often associated with severe toxicity and the presence of a greyish-white, leathery pseudomembrane over the tonsils and pharynx. **Analysis of Incorrect Options:** * **Hamartoma of Lung (Option A):** This is a benign neoplastic growth in the lung. Radiologically, it is characterized by "Popcorn calcification," not cervical swelling. * **Glaucoma (Option C):** This refers to increased intraocular pressure. Congenital glaucoma is associated with "Buphthalmos" (ox-eye), which affects the globe of the eye, not the neck. * **Hepatic Candidiasis (Option D):** This is a fungal infection of the liver, typically seen in immunocompromised patients. On imaging (CT/USG), it presents with a "Bull’s eye" appearance (target lesions), which is a radiologic sign, not a clinical neck deformity. **Clinical Pearls for NEET-PG:** * **Causative Agent:** *Corynebacterium diphtheriae* (Gram-positive, club-shaped bacilli, showing Chinese-letter pattern). * **Culture Media:** Löffler's serum slope (rapid growth) and Potassium Tellurite agar (black colonies). * **Schick Test:** Used to determine the immune status of an individual toward diphtheria. * **Complications:** Myocarditis (most common cause of death) and neurological involvement (Palatal palsy). * **Treatment:** Prompt administration of Diphtheria Antitoxin (DAT) and antibiotics (Penicillin or Erythromycin).

Q: A 6-year-old girl complains of otalgia, fever, and irritability. Physical examination reveals a stiff, bulging, red tympanic membrane. Previous history of ear infections is denied. What is the recommended duration of antibiotic treatment for acute otitis media in this patient?

5 days. **Explanation:** The patient presents with classic features of **Acute Otitis Media (AOM)**: otalgia, fever, and a bulging, erythematous tympanic membrane. The duration of antibiotic therapy in AOM is determined primarily by the **age of the patient** and the **severity of the disease**. **Why Option B is correct:** Current clinical guidelines (AAP and IAP) recommend a shortened course of antibiotics for older children with uncomplicated AOM. For children **aged 6 years and older** with mild-to-moderate symptoms, a **5-day course** of antibiotics (typically Amoxicillin) is considered adequate and effective. This shorter duration improves compliance and reduces the risk of antibiotic resistance and side effects. **Analysis of Incorrect Options:** * **Option A (1 day):** A single dose is insufficient to eradicate common pathogens like *S. pneumoniae* or *H. influenzae*. * **Option C (7 days):** This is generally recommended for children aged **2 to 5 years** with mild-to-moderate AOM. * **Option D (10 days):** This is the standard duration for **children 39°C), or those with perforated membranes/recurrent infections. **Clinical Pearls for NEET-PG:** * **First-line Drug:** High-dose **Amoxicillin** (80–90 mg/kg/day) is the treatment of choice. * **Diagnosis:** The most specific sign of AOM is **bulging of the tympanic membrane** (indicates middle ear effusion + inflammation). * **Watchful Waiting:** In children >6 months with unilateral, non-severe AOM, "watchful waiting" for 48–72 hours is an option before starting antibiotics. * **Common Pathogens:** *Streptococcus pneumoniae* (most common), Non-typeable *Haemophilus influenzae*, and *Moraxella catarrhalis*.

Q: Which of the following is a late toxic manifestation of diphtheria in a child?

Myocarditis. **Explanation:** **Diphtheria**, caused by *Corynebacterium diphtheriae*, is primarily a toxin-mediated disease. The **exotoxin** (produced by lysogenic bacteriophage) inhibits protein synthesis, leading to local tissue necrosis (pseudomembrane) and systemic complications. **Why Myocarditis is the Correct Answer:** Myocarditis is the most common and serious **late toxic manifestation**, typically occurring during the **second week** of the illness as the toxin binds to cardiac myocytes. It presents with arrhythmias, heart blocks, or congestive heart failure. It is a major cause of mortality in diphtheria patients. **Analysis of Incorrect Options:** * **Renal Failure (A):** While the toxin can cause acute tubular necrosis (ATN) leading to proteinuria or mild renal impairment, frank renal failure is not a classic or primary toxic manifestation compared to cardiac or neurological involvement. * **Septicemia (D):** Diphtheria is essentially a **toxemia**, not a bacteremia. The bacteria remain localized in the upper respiratory tract or skin; the systemic damage is caused by the circulating toxin, not the spread of the bacteria in the bloodstream. * **None of the above (C):** Incorrect, as myocarditis is a well-documented toxic complication. **High-Yield Clinical Pearls for NEET-PG:** * **Biphasic Course:** Toxic manifestations often follow a biphasic pattern: **Myocarditis** (Week 2) followed by **Neurological complications** (Weeks 3–6, e.g., palatal palsy, ciliary paralysis, or Guillain-Barré-like polyneuropathy). * **Diagnosis:** Culture on **Löffler’s serum slope** or **Potassium Tellurite agar** (black colonies). Toxin production is confirmed by the **Elek test**. * **Treatment:** Immediate administration of **Diphtheria Antitoxin (DAT)** is the mainstay of therapy; antibiotics (Penicillin or Erythromycin) are used only to stop further toxin production and prevent spread.

Q: Rubella infection is known to cause all of the following congenital anomalies except:

Aortic Stenosis (AS). **Explanation:** Congenital Rubella Syndrome (CRS) is a classic "TORCH" infection characterized by a specific triad of clinical findings: **Cataracts, Sensorineural deafness, and Cardiac defects.** **1. Why Aortic Stenosis (AS) is the Correct Answer:** While Rubella causes several cardiovascular malformations, **Aortic Stenosis** is not typically associated with the syndrome. Aortic Stenosis is more commonly linked to conditions like Turner Syndrome or Williams Syndrome (Supravalvular AS). In CRS, the primary cardiac pathologies involve the great vessels and the right side of the heart. **2. Analysis of Incorrect Options:** * **Patent Ductus Arteriosus (PDA):** This is the **most common** cardiac anomaly in Rubella. The virus inhibits the normal development of the vascular endothelium, preventing the physiological closure of the ductus. * **Microcephaly:** CRS is a neurodevelopmental teratogen. It causes intrauterine growth restriction (IUGR) and interferes with brain growth, leading to microcephaly, mental retardation, and "salt and pepper" retinopathy. * **Ventricular Septal Defect (VSD):** While PDA and Peripheral Pulmonary Artery Stenosis are more specific, VSD is a recognized component of the structural heart defects seen in CRS. **3. NEET-PG High-Yield Pearls:** * **Gregg’s Triad:** Cataracts, Deafness, and Heart disease (PDA). * **Classic Skin Finding:** "Blueberry muffin" spots (due to extramedullary hematopoiesis). * **Most Common Defect:** Sensorineural hearing loss is the most frequent overall sign. * **Timing:** Risk is highest if infection occurs during the **first trimester** (especially the first 8 weeks). * **Diagnosis:** Confirmed by Rubella-specific IgM in the newborn or persistent IgG levels beyond 6 months.

Question 1

A child presents with fever, conjunctival redness, and bluish -white spots on the buccal mucosa. What is the most likely diagnosis?

Accepted Answer

Measles

Answer

Mumps

Answer

Chickenpox

Answer

Rubella

Question 2

A child presents with fever, altered level of consciousness, and signs of meningeal irritation.
Cerebrospinal fluid (CSF) analysis reveals the following findings:
- Cell differential: Predominantly lymphocytes
- Protein: Elevated
- Glucose: Low
Based on these CSF findings, what is the most likely diagnosis?

Accepted Answer

Tuberculous meningitis

Answer

Pyogenic (bacterial) meningitis

Answer

Viral meningitis

Answer

Fungal meningitis

Question 3

Which of the following is NOT a recognized diagnostic feature of Kawasaki disease?

Accepted Answer

Purulent conjunctivitis

Answer

Non-purulent (bilateral) conjunctivitis

Answer

Cervical lymphadenopathy

Answer

Fever lasting more than 5 days

Question 4

A 6-week-old infant with prolonged NICU stay with presentation of fever, lethargy, poor feeding
with CSF analysis showing features of bacterial meningitis. Which of the following are responsible?
a. Staphylococcus aureus
b. Hemophilus influenzae
c. Streptococcus pneumoniae
d. Listeria
Choose the correct answer:

Accepted Answer

All of the above

Answer

Listeria

Answer

b and d

Answer

a, b, d

Question 5

Sternal edema is seen in which of the following conditions?

Accepted Answer

Mumps

Answer

Measles

Answer

Diphtheria

Answer

Varicella

Question 6

What is NOT a common cause of meningitis in an 8-year-old child?

Accepted Answer

Staphylococcus aureus

Answer

Streptococcus pneumoniae

Answer

Haemophilus influenzae

Answer

Neisseria meningitidis

Question 7

Bull's neck is characteristically seen in which of the following conditions?

Accepted Answer

Diphtheria

Answer

Hamartoma of Lung

Answer

Glaucoma

Answer

Hepatic Candidiasis

Question 8

A 6-year-old girl complains of otalgia, fever, and irritability. Physical examination reveals a stiff, bulging, red tympanic membrane. Previous history of ear infections is denied. What is the recommended duration of antibiotic treatment for acute otitis media in this patient?

Accepted Answer

5 days

Answer

1 day

Answer

7 days

Answer

10 days

Question 9

Which of the following is a late toxic manifestation of diphtheria in a child?

Accepted Answer

Myocarditis

Answer

Renal failure

Answer

None of the above

Answer

Septicemia

Question 10

Rubella infection is known to cause all of the following congenital anomalies except:

Accepted Answer

Aortic Stenosis (AS)

Answer

Microcephaly

Answer

Ventricular Septal Defect (VSD)

Answer

Patent Ductus Arteriosus (PDA)

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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