Infectious Diseases Practice Questions

Q: What is the most common manifestation of congenital toxoplasmosis?

Chorioretinitis. **Explanation:** Congenital Toxoplasmosis is caused by the transplacental transmission of *Toxoplasma gondii*. While many neonates are asymptomatic at birth, **Chorioretinitis** is the most common clinical manifestation overall. It occurs in approximately 75-80% of affected children, often presenting as blurred vision or strabismus later in life, even if the child appeared normal at birth. **Analysis of Options:** * **B. Chorioretinitis (Correct):** It is the most frequent finding and is often bilateral. It represents the "late" manifestation of the infection and is part of the classic Sabin’s Triad. * **A. Hydrocephalus:** This is a classic feature (part of the triad) but is less common than chorioretinitis. It typically results from obstructive aqueductal stenosis. * **C. Calcification:** Specifically **intracranial diffuse calcifications**. While highly characteristic of Toxoplasmosis (distinguishing it from the periventricular calcifications of CMV), they occur in only about 50-60% of symptomatic cases. * **D. Convulsions:** These are a secondary neurological complication resulting from intracranial damage/calcifications but are not the primary or most common diagnostic sign. **High-Yield Pearls for NEET-PG:** 1. **Sabin’s Triad:** Chorioretinitis, Hydrocephalus, and Intracranial Calcifications. 2. **Calcification Pattern:** Diffuse/Scattered (Toxoplasmosis) vs. Periventricular (CMV). 3. **Transmission Risk:** The risk of transmission increases with gestational age (highest in the 3rd trimester), but the **severity** of fetal damage is highest if infected in the 1st trimester. 4. **Treatment:** Spiramycin (to prevent transmission) or Pyrimethamine + Sulfadiazine + Folinic acid (for fetal/neonatal infection).

Q: Use of aspirin in children with viral disease is associated with which of the following?

Reye's syndrome. **Explanation:** The correct answer is **B. Reye's syndrome**. **Why it is correct:** Reye's syndrome is a rare but life-threatening condition characterized by **acute encephalopathy** and **fatty degeneration of the liver**. It is strongly associated with the administration of **aspirin (salicylates)** to children or adolescents during a viral illness, most commonly **Influenza B** or **Varicella (Chickenpox)**. The underlying pathophysiology involves **mitochondrial dysfunction**, leading to impaired fatty acid oxidation and hyperammonemia. **Why other options are incorrect:** * **A. Metabolic acidosis:** While salicylate toxicity (aspirin overdose) causes a mixed respiratory alkalosis and metabolic acidosis, it is not the specific syndrome associated with pediatric viral infections. * **C. Renal tubular acidosis (RTA):** RTA is a group of disorders involving the kidneys' inability to maintain acid-base balance. It is not linked to aspirin use in viral prodromes. * **D. Fixed drug eruption:** This is a localized cutaneous drug reaction that recurs at the same site upon re-exposure to a drug (e.g., NSAIDs, sulfonamides), but it is not the classic association described here. **High-Yield Clinical Pearls for NEET-PG:** * **Biochemical Hallmarks:** Elevated serum ammonia, prolonged Prothrombin Time (PT/INR), and elevated AST/ALT with **normal bilirubin**. * **Liver Biopsy Findings:** Microvesicular steatosis (small fat droplets in hepatocytes) without significant inflammation. * **Management:** Supportive care, focusing on managing cerebral edema (Mannitol) and correcting hypoglycemia. * **Prevention:** Use **Acetaminophen (Paracetamol)** or Ibuprofen instead of aspirin in children with fever. *Exception:* Aspirin is still used in pediatrics for **Kawasaki disease** and **Rheumatic fever**.

Q: Parotitis and orchitis are common manifestations of which disease?

Mumps. **Explanation:** **Mumps** is an acute viral infection caused by the **Rubulavirus** (Paramyxoviridae family). It is characterized by a predilection for glandular and nervous tissues. 1. **Why Mumps is correct:** * **Parotitis:** The most common clinical manifestation (95% of symptomatic cases), typically presenting as painful, usually bilateral swelling of the parotid glands. * **Orchitis:** The most common complication in post-pubertal males (occurring in up to 30-40% of cases). It is usually unilateral and can lead to testicular atrophy, though permanent infertility is rare. 2. **Why other options are incorrect:** * **Diphtheria:** Caused by *Corynebacterium diphtheriae*, it presents with a "bull-neck" appearance due to cervical lymphadenopathy and a greyish pseudomembrane in the pharynx. It does not cause parotitis or orchitis. * **Measles (Rubeola):** Characterized by the 3 C’s (Cough, Coryza, Conjunctivitis), Koplik spots, and a maculopapular rash. Common complications include pneumonia and SSPE. * **Rubella (German Measles):** Presents with a milder rash and significant **post-auricular and suboccipital lymphadenopathy**, not parotid swelling. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication in children:** Aseptic meningitis. * **Most common cause of acquired sensorineural deafness** in children is Mumps (usually unilateral). * **Pancreatitis** is another classic glandular manifestation of Mumps. * **Diagnosis:** Clinical diagnosis is standard; elevated **Serum Amylase** is a key laboratory finding due to parotid involvement. * **Prevention:** Live attenuated vaccine (Jeryl Lynn strain) as part of the MMR vaccine.

Q: What is the most common cause of diarrhea in children?

Rotavirus. **Explanation:** **Rotavirus** is the most common cause of severe, dehydrating diarrhea in children worldwide, particularly in those under 5 years of age. It primarily affects the mature enterocytes at the tips of the intestinal villi, leading to malabsorption and osmotic diarrhea. In India, despite the introduction of the Rotavirus vaccine in the Universal Immunization Programme (UIP), it remains a leading cause of pediatric morbidity. **Analysis of Options:** * **Vibrio cholerae (Option A):** While it causes severe "rice-water" stools and rapid dehydration, it occurs more in epidemic patterns rather than being the most common cause of routine pediatric diarrhea. * **E. coli (Option B):** Enterotoxigenic *E. coli* (ETEC) is a frequent cause of "traveler’s diarrhea" and is common in developing countries, but globally, viral etiologies (specifically Rotavirus) outnumber bacterial causes in the pediatric age group. * **Pneumococcus (Option D):** *Streptococcus pneumoniae* is a leading cause of pneumonia, meningitis, and otitis media in children, but it is not a primary gastrointestinal pathogen. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Rotavirus produces the **NSP4 enterotoxin**, which induces secretory diarrhea by increasing intracellular calcium. * **Seasonality:** In temperate climates, it peaks in winter; in India, it is seen year-round with a peak in the cooler months (October–February). * **Diagnosis:** The gold standard for rapid detection is **ELISA** or Latex Agglutination for Rotavirus antigen in stools. * **Vaccination:** Two main vaccines are used—**Rotarix** (Monovalent, 2 doses) and **RotaTeq/Rotavac** (Pentavalent/Multivalent, 3 doses). In the National Schedule, Rotavac is given at 6, 10, and 14 weeks.

Q: Which vaccines are not recommended for an 8-year-old unimmunized child?

All of the above. **Explanation:** The correct answer is **D. All of the above**, based on the age-specific recommendations for immunization in older children. 1. **Pertussis (Option A):** The whole-cell Pertussis vaccine (wP) is generally not recommended for children above **7 years of age** due to an increased risk of severe local and systemic reactions (fever, soreness). In older children and adults, the acellular form with reduced antigen content (**Tdap**) is preferred over the standard DTwP/DTaP. 2. **Salk vaccine (IPV) (Option B):** According to the National Immunization Schedule (NIS) and WHO guidelines, the primary focus for Polio vaccination is children under 5 years. In an unimmunized 8-year-old, the risk of Vaccine-Associated Paralytic Polio (VAPP) and the epidemiological shift make routine IPV less of a priority compared to the primary series in infancy, though some private guidelines (IAP) may offer it up to age 18 in specific catch-up scenarios. 3. **BCG vaccine (Option C):** BCG is most effective in preventing severe forms of childhood tuberculosis (miliary and meningeal TB). It is recommended at birth or up to **1 year of age** under the National Immunization Schedule. Beyond age 1, its protective efficacy diminishes significantly, and it is generally not recommended for an 8-year-old. **High-Yield Clinical Pearls for NEET-PG:** * **Age Cut-off for DTwP:** 7 years. Use Tdap for catch-up in older children. * **BCG Limit:** 1 year (National Schedule); however, some guidelines allow it up to 5 years if the child is Mantoux negative, but never routinely at age 8. * **Catch-up Immunization:** For a child >7 years, the standard catch-up includes Td (Tetanus-Diphtheria), Hepatitis B, and MMR. * **Live Vaccines:** Always contraindicated in pregnancy and severe immunocompromised states (except HIV with CD4 >15%).

Q: Koplik spots are pathognomonic of which disease?

Measles. **Explanation:** **Koplik spots** are considered the **pathognomonic** (diagnostic) sign of **Measles (Rubeola)**. They are small, irregular, bluish-white spots on an erythematous base, often described as "grains of salt on a red background." 1. **Why Option A is correct:** Koplik spots are unique to Measles. They appear during the **prodromal phase**, approximately 48 hours before the characteristic maculopapular rash develops. Their presence allows for a definitive clinical diagnosis even before the rash appears. 2. **Why Option B and C are incorrect (in the context of the question):** While Option B describes the correct location and Option C describes the correct timing, the question asks which **disease** they are pathognomonic of. Therefore, "Measles" is the specific answer required. (Note: In some MCQ formats, if the question asks "Which of the following is true regarding Koplik spots?", "All of the above" might be correct, but here the focus is the disease entity). **High-Yield Clinical Pearls for NEET-PG:** * **Location:** Most commonly found on the buccal mucosa opposite the **lower second molars** (though they can spread). * **Timeline:** They appear 2 days before the rash and typically disappear within 1–2 days after the rash starts. * **Measles Triad (3 C's):** Cough, Coryza, and Conjunctivitis (seen in the prodromal phase). * **Rash Progression:** The Measles rash is cephalocaudal (starts behind the ears/hairline and spreads downwards) and fades with brownish discoloration and desquamation. * **Vitamin A:** Supplementation is recommended for all children with Measles to reduce morbidity and mortality.

Q: A 3-year-old child presents with symptoms of influenza. Aspirin is contraindicated in this patient due to the increased risk of which of the following conditions?

Reye's syndrome. ### Explanation **Correct Answer: D. Reye's syndrome** **Mechanism and Rationale:** Reye’s syndrome is a rare but life-threatening condition characterized by **acute encephalopathy** and **fatty degeneration of the liver**. It is strongly associated with the use of **salicylates (Aspirin)** in children and adolescents during viral prodromes, most commonly **Influenza (Type B)** and **Varicella (Chickenpox)**. The underlying pathophysiology involves **mitochondrial dysfunction**, leading to impaired fatty acid oxidation. This results in hyperammonemia and cerebral edema. Clinically, it presents with protracted vomiting followed by altered mental status, seizures, and hepatomegaly without jaundice. **Analysis of Incorrect Options:** * **A. Gastric bleeding:** While aspirin causes gastric irritation and bleeding in adults due to COX-1 inhibition, it is not the primary reason for its absolute contraindication in pediatric viral infections. * **B. Thrombocytopenia:** Aspirin causes irreversible inhibition of platelet aggregation (anti-platelet effect), but it does not typically cause a decrease in the absolute platelet count (thrombocytopenia). * **C. Fanconi syndrome:** This is a disorder of proximal renal tubular function. While certain drugs (like expired tetracycline or cisplatin) can cause it, aspirin is not a recognized trigger. **High-Yield Clinical Pearls for NEET-PG:** * **Biochemical Hallmarks:** Elevated serum ammonia, prolonged Prothrombin Time (PT/INR), and elevated AST/ALT with **normal bilirubin**. * **Liver Biopsy Findings:** Microvesicular steatosis (small fat droplets in hepatocytes). * **Exceptions:** Aspirin is still used in children for specific conditions like **Kawasaki Disease** and **Juvenile Idiopathic Arthritis (JIA)**, under strict supervision. * **Drug of Choice:** Acetaminophen (Paracetamol) or Ibuprofen are the preferred antipyretics in children with viral fever.

Q: Which of the following is a characteristic feature of Henoch-Schönlein Purpura?

Blood in stool. **Explanation:** **Henoch-Schönlein Purpura (HSP)**, now commonly termed IgA Vasculitis, is the most common systemic vasculitis in children. It is a small-vessel vasculitis characterized by the deposition of **IgA-dominant immune complexes**. **Why "Blood in stool" is correct:** Gastrointestinal involvement occurs in approximately 75% of patients. The vasculitis affects the splanchnic circulation, leading to mucosal edema and submucosal hemorrhage. This clinically manifests as colicky abdominal pain, vomiting, and **hematochezia (blood in stool)** or melena. A significant complication to remember for exams is **ileo-colic intussusception**, where the submucosal hemorrhage acts as a lead point. **Analysis of Incorrect Options:** * **B. Thrombocytopenia:** HSP is a **non-thrombocytopenic purpura**. In fact, the platelet count is typically normal or even elevated (as an acute phase reactant). This is a crucial diagnostic differentiator from Immune Thrombocytopenic Purpura (ITP). * **C. Intracranial hemorrhage:** While serious, this is an extremely rare complication of HSP. It is more commonly associated with severe thrombocytopenia (like ITP) or vascular malformations. * **D. Susceptibility to infection:** HSP is an immune-mediated reaction (often following a URI), not an immunodeficiency state. **NEET-PG High-Yield Pearls:** * **Classic Tetrad:** Palpable purpura (without thrombocytopenia), Arthritis/Arthralgia, Abdominal pain, and Renal involvement (Hematuria). * **Skin:** Purpura is typically distributed over dependent areas (buttocks and lower extremities). * **Renal:** HSP Nephritis is histologically identical to **IgA Nephropathy (Berger’s disease)**. * **Diagnosis:** Primarily clinical; Biopsy (if done) shows **Leukocytoclastic vasculitis** with IgA deposits on immunofluorescence.

Question 1

What is the most common manifestation of congenital toxoplasmosis?

Accepted Answer

Chorioretinitis

Answer

Hydrocephalus

Answer

Calcification

Answer

Convulsions

Question 2

Use of aspirin in children with viral disease is associated with which of the following?

Accepted Answer

Reye's syndrome

Answer

Metabolic acidosis

Answer

Renal tubular acidosis

Answer

Fixed drug eruption

Question 3

Parotitis and orchitis are common manifestations of which disease?

Accepted Answer

Mumps

Answer

Diphtheria

Answer

Measles

Answer

Rubella

Question 4

What is the most common cause of diarrhea in children?

Accepted Answer

Rotavirus

Answer

Vibrio cholera

Answer

E. coli

Answer

Pneumococcus

Question 5

An 8-year-old child presents with acute lymphadenopathy and fever, and laboratory findings show 20% lymphocytosis. What is the most likely diagnosis?

Accepted Answer

Infectious mononucleosis

Answer

Acute lymphoblastic leukemia (ALL)

Answer

Pulmonary tuberculosis (Koch's)

Answer

Alpha-hemolytic streptococcal infection

Question 6

Which of the following is NOT a contraindication to DPT vaccination?

Accepted Answer

Local reaction to a previous DPT dose

Answer

High fever following a previous DPT dose

Answer

Infantile spasms

Answer

Seizures after a previous DPT dose

Question 7

Which vaccines are not recommended for an 8-year-old unimmunized child?

Accepted Answer

All of the above

Answer

Pertussis

Answer

Salk vaccine

Answer

BCG vaccine

Question 8

Koplik spots are pathognomonic of which disease?

Accepted Answer

Measles

Answer

Present on the buccal mucosa opposite the upper molars

Answer

Always present in the prodromal phase

Answer

All of the above

Question 9

A 3-year-old child presents with symptoms of influenza. Aspirin is contraindicated in this patient due to the increased risk of which of the following conditions?

Accepted Answer

Reye's syndrome

Answer

Gastric bleeding

Answer

Thrombocytopenia

Answer

Fanconi syndrome

Question 10

Which of the following is a characteristic feature of Henoch-Schönlein Purpura?

Accepted Answer

Blood in stool

Answer

Thrombocytopenia

Answer

Intracranial hemorrhage

Answer

Susceptibility to infection

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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