Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 51: What is the recommended dose of oseltamivir for chemoprophylaxis in an infant?

A. 3 mg/kg once daily (Correct Answer)
B. 20 mg once a day
C. 20 mg twice a day
D. 20 mg thrice a day

Explanation: **Explanation:** The correct answer is **A. 3 mg/kg once daily**. **Medical Concept:** Oseltamivir is a neuraminidase inhibitor used for both the treatment and chemoprophylaxis of Influenza A and B. In infants (aged 0–12 months), the dosing is weight-based rather than age-based due to the rapid physiological changes in renal clearance during the first year of life. For **chemoprophylaxis**, the standard recommendation is **3 mg/kg administered once daily** for 7–10 days following exposure. **Analysis of Options:** * **Option A (Correct):** 3 mg/kg once daily is the established prophylactic dose for infants to prevent the onset of symptoms after exposure. * **Option B, C, and D (Incorrect):** These options provide fixed doses (20 mg). While 30 mg, 45 mg, 60 mg, and 75 mg are standard fixed doses for older children and adults based on weight bands, infants require precise mg/kg dosing. Furthermore, "thrice a day" (Option D) is never a standard frequency for oseltamivir, which is typically dosed once daily (prophylaxis) or twice daily (treatment). **High-Yield Clinical Pearls for NEET-PG:** * **Treatment vs. Prophylaxis:** For infants, the **treatment** dose is 3 mg/kg **twice daily** for 5 days, whereas **prophylaxis** is **once daily**. * **Age Limit:** Oseltamivir is FDA-approved for treatment from birth and for prophylaxis from 3 months of age (though used off-label in younger infants during outbreaks). * **Mechanism of Action:** It inhibits the neuraminidase enzyme, preventing the release of new virions from infected host cells. * **Timing:** To be most effective, oseltamivir should be started within **48 hours** of symptom onset or exposure.

Question 52: Which of the following is true about the triad of congenital rubella syndrome?

A. Patent ductus arteriosus, cataract, and deafness are seen. (Correct Answer)
B. Hepatosplenomegaly, mental retardation, and deafness are seen.
C. Chorioretinitis, multiorgan failure, and pneumonitis are seen.
D. None of the above.

Explanation: The classic triad of **Congenital Rubella Syndrome (CRS)**, also known as **Gregg’s Triad**, is a high-yield topic for NEET-PG. It occurs when the rubella virus crosses the placenta, primarily during the first trimester, interfering with organogenesis. ### **Explanation of the Correct Answer** **Option A** is correct because the classic triad consists of: 1. **Cardiac Defects:** Most commonly **Patent Ductus Arteriosus (PDA)**, followed by peripheral pulmonary artery stenosis. 2. **Eye Defects:** Characteristically **Cataracts** (often bilateral with a "ground-glass" appearance) and microphthalmia. 3. **Ear Defects:** **Sensorineural Hearing Loss (SNHL)**, which is the most common manifestation of CRS overall. ### **Explanation of Incorrect Options** * **Option B:** While hepatosplenomegaly and intellectual disability can occur in CRS, they are not part of the defining "classic triad." * **Option C:** Chorioretinitis is more characteristic of **Congenital Toxoplasmosis**. While CRS can cause "salt and pepper" retinopathy, it rarely causes exudative chorioretinitis. Pneumonitis and multiorgan failure are complications of neonatal sepsis or severe CMV, rather than the primary CRS triad. ### **High-Yield Clinical Pearls for NEET-PG** * **Salt and Pepper Retinopathy:** The most common ocular finding in CRS (though cataracts are the triad component). * **Blueberry Muffin Rash:** Caused by extramedullary hematopoiesis (also seen in CMV). * **Radiology:** Look for **"Celery Stalk" appearance** (longitudinal radiolucent striations) in the metaphysis of long bones. * **Timing:** The risk of malformation is highest (up to 80%) if the mother is infected within the first **12 weeks** of gestation. * **Diagnosis:** Confirmed by Rubella-specific **IgM antibodies** in the newborn or persistence of IgG beyond 6–12 months.

Question 53: A child's CSF was examined and showed slightly raised or normal PMN cells, raised lymphocytes, absence of mycotic growth, normal or above normal protein value, and normal glucose level. What is the most probable diagnosis?

A. Pyogenic bacterial meningitis
B. Viral meningitis (Correct Answer)
C. Fungal meningitis
D. Tuberculous meningitis

Explanation: ### Explanation The clinical presentation of cerebrospinal fluid (CSF) analysis is a high-yield topic for NEET-PG. The diagnosis of **Viral Meningitis** (Aseptic Meningitis) is based on the following characteristic CSF findings: 1. **Glucose Level:** This is the most critical differentiator. In viral meningitis, glucose is **normal** (typically >2/3rd of blood glucose), whereas it is significantly decreased in bacterial, fungal, and tuberculous meningitis. 2. **Cellular Profile:** There is a predominance of **lymphocytes**. While PMNs (polymorphonuclear cells) may be slightly raised in the very early stages (first 24 hours), the shift to lymphocytosis is classic. 3. **Protein:** Protein levels are usually **normal or mildly elevated** (typically <100 mg/dL), unlike the marked elevations seen in other types. #### Why the other options are incorrect: * **Pyogenic Bacterial Meningitis:** Characterized by marked **neutrophilic pleocytosis**, significantly **low glucose** (<40 mg/dL), and very high protein levels. * **Tuberculous Meningitis (TBM):** While it shows lymphocytosis, the **glucose is always low** and the protein is characteristically very high (often causing a cobweb coagulum). * **Fungal Meningitis:** Similar to TBM, it presents with low glucose and elevated protein. The question also specifically mentions the **absence of mycotic growth**. #### NEET-PG High-Yield Pearls: * **Most common cause of Viral Meningitis:** Enteroviruses (Coxsackie and Echovirus). * **Normal CSF Glucose:** 40–70 mg/dL (or 60-70% of plasma glucose). * **Normal CSF Protein:** 15–45 mg/dL. * **Mnemonic for TBM:** "Low Sugar, High Protein, Lymphocytes" (The "T" in TBM stands for "Tiny sugar").

Question 54: Mumps is characterized by a triad of which of the following?

A. Epidemic parotitis, orchitis-oophoritis, pancreatitis. (Correct Answer)
B. Orchitis-oophoritis, encephalitis, pancreatitis.
C. Epidemic parotitis, meningoencephalitis, pancreatitis.
D. None of the above.

Explanation: **Explanation:** Mumps is an acute viral infection caused by the **Rubulavirus** (Paramyxoviridae family). It is characterized by its affinity for glandular and neurological tissues. The classic clinical triad of Mumps consists of **Epidemic parotitis, Orchitis/Oophoritis, and Pancreatitis**. 1. **Why Option A is correct:** The virus primarily replicates in the upper respiratory tract and then spreads hematogenously to target organs. * **Parotitis:** The most common manifestation (95% of symptomatic cases), usually bilateral. * **Orchitis/Oophoritis:** The most common extra-salivary site in post-pubertal males (orchitis is usually unilateral). * **Pancreatitis:** Presents as epigastric pain and vomiting; it is a classic component of the triad, though often mild. 2. **Why other options are incorrect:** * **Option B & C:** While **Meningoencephalitis** is the most common *neurological* complication of Mumps (often presenting as aseptic meningitis), it is not traditionally considered part of the "triad" of glandular involvement that defines the classic presentation in medical literature and competitive exams. **High-Yield Clinical Pearls for NEET-PG:** * **Incubation Period:** 14–21 days (Average 18 days). * **Infectivity:** Maximum 48 hours *before* the onset of parotitis. * **Diagnosis:** Primarily clinical; however, **Serum Amylase** is elevated in both parotitis and pancreatitis. * **Complications:** * Most common complication in children: **Aseptic meningitis**. * Most common cause of **acquired sensorineural deafness** in children (usually unilateral). * **Prevention:** Live attenuated vaccine (Jeryl Lynn strain) as part of the MMR vaccine.

Question 55: Regarding primary complex in children, all are true except?

A. Effusion is seen
B. Consolidation is present
C. Fibrosis
D. None of the above (Correct Answer)

Explanation: ### Explanation The **Primary Complex** (also known as the Ghon complex) is the hallmark of primary tuberculosis in children. It consists of three components: a parenchymal lesion (Ghon focus), lymphangitis, and regional lymphadenopathy. **Why "None of the above" is correct:** The question asks which of the listed features is **NOT** seen in a primary complex. However, all the listed options (A, B, and C) are recognized components or potential outcomes of primary pulmonary tuberculosis in children. Therefore, none of the statements are false. * **Option A (Effusion):** Pleural effusion is a common manifestation of primary TB in children, often resulting from a hypersensitivity reaction to the tubercle bacilli or direct extension from a subpleural focus. * **Option B (Consolidation):** The Ghon focus itself is an area of subpleural inflammatory consolidation. In children, this can sometimes involve an entire lobe (epituberculosis) due to bronchial compression by enlarged lymph nodes. * **Option C (Fibrosis):** The natural history of a primary complex involves healing. Most primary lesions undergo healing by **fibrosis** and subsequent calcification (Ranke Complex). **High-Yield Clinical Pearls for NEET-PG:** * **Ghon Focus:** Usually located in the subpleural region of the upper part of the lower lobe or lower part of the upper lobe. * **Ranke Complex:** A healed primary complex that has undergone calcification (visible on X-ray). * **Epituberculosis:** A wedge-shaped collapse-consolidation seen in children, caused by extrinsic compression of a bronchus by tubercular lymph nodes. * **Progressive Primary TB:** Unlike adults, children are more prone to hematogenous spread (Miliary TB) or local progression if the immune response is inadequate.

Question 56: What are the complications of meningitis in a child?

A. Arachnoiditis (Correct Answer)
B. Mental retardation
C. Status epilepticus
D. Sensorineural hearing loss

Explanation: **Explanation:** In the context of pediatric meningitis, while all the options listed are potential sequelae, **Arachnoiditis** is a classic pathological complication involving the inflammation of the leptomeninges. In bacterial meningitis, the inflammatory exudate often accumulates at the base of the brain, leading to adhesive arachnoiditis. This can obstruct the flow of cerebrospinal fluid (CSF), resulting in **obstructive hydrocephalus** and cranial nerve palsies. **Analysis of Options:** * **Arachnoiditis (Correct):** This represents the direct inflammatory extension of the disease. It is a hallmark pathological finding in chronic or severe bacterial meningitis (especially Tubercular Meningitis). * **Mental Retardation (Incorrect):** Now more appropriately termed Intellectual Disability, this is a long-term neurodevelopmental *sequela* rather than an acute pathological complication. * **Status Epilepticus (Incorrect):** While seizures occur in about 20-30% of cases, status epilepticus is a clinical *presentation* or acute neurological emergency rather than a structural complication of the meningeal layers. * **Sensorineural Hearing Loss (SNHL) (Incorrect):** SNHL is the **most common permanent sequela** of bacterial meningitis in children (occurring in ~10% of cases), often due to labyrinthitis ossificans. However, it is a functional deficit rather than a primary meningeal complication like arachnoiditis. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication overall:** Subdural effusion (especially in infants with *H. influenzae*). * **Most common permanent sequela:** Sensorineural hearing loss (SNHL). * **Waterhouse-Friderichsen Syndrome:** Adrenal hemorrhage associated with Meningococcemia. * **SIADH:** A common metabolic complication leading to hyponatremia in pediatric meningitis.

Question 57: A 10-year-old boy presents with jaundice, dark urine, and abdominal discomfort. Liver function tests reveal serum transaminase levels of 2100 IU/L. Which of the following is the most accurate statement about probable complications?

A. Significant likelihood of hepatocellular carcinoma
B. About a 10 percent chance of a chronic carrier state
C. Almost no chance of long-term sequelae (Correct Answer)
D. Long-term complications require interferon therapy

Explanation: ### Explanation **Core Concept: Hepatitis A in Children** The clinical presentation of jaundice, dark urine, and markedly elevated transaminases (>1000 IU/L) in a 10-year-old is classic for **Hepatitis A Virus (HAV)** infection. In the pediatric age group, HAV is the most common cause of acute viral hepatitis. **Why Option C is Correct:** Hepatitis A is an acute, self-limiting illness transmitted via the fecal-oral route. Unlike Hepatitis B or C, **HAV never progresses to chronic hepatitis, a permanent carrier state, or cirrhosis.** Therefore, once the acute episode resolves, there is almost no chance of long-term sequelae. Recovery provides lifelong immunity. **Analysis of Incorrect Options:** * **Option A:** Hepatocellular carcinoma (HCC) is a complication of *chronic* viral hepatitis (HBV, HCV, or HDV). Since HAV does not cause chronic infection, it does not increase the risk of HCC. * **Option B:** A chronic carrier state is characteristic of HBV (especially when acquired at birth) and HCV. HAV does not have a carrier state. * **Option D:** Interferon therapy is used for managing chronic Hepatitis B and C. Management for HAV is purely supportive (hydration and nutrition), as the body clears the virus spontaneously. **NEET-PG High-Yield Pearls:** * **Transmission:** Fecal-oral route (contaminated water/food). * **Diagnosis:** Acute infection is confirmed by **Anti-HAV IgM**. Anti-HAV IgG indicates past infection or vaccination. * **Extrahepatic Manifestations:** Though rare, HAV can cause evanescent rashes or arthralgia. * **Fulminant Hepatic Failure:** While HAV doesn't go chronic, it can rarely cause acute liver failure (more common in adults than children). * **Vaccination:** Two doses are given 6 months apart (starting after 1 year of age).

Question 58: A boy presents with multiple bullous lesions on his trunk and periostitis observed on x-rays. What is the most appropriate next investigation?

A. VDRL testing for mother and child (Correct Answer)
B. PCR for maternal tuberculosis
C. HBsAg screening
D. ELISA testing for mother and child

Explanation: ### Explanation The clinical presentation of **bullous lesions** (Pemphigus syphiliticus) and **periostitis** in an infant is highly suggestive of **Congenital Syphilis**. **1. Why Option A is Correct:** Congenital syphilis is caused by the transplacental transmission of *Treponema pallidum*. The classic early manifestations (appearing before age 2) include: * **Cutaneous signs:** Vesiculobullous lesions (often on palms and soles) or a maculopapular rash. * **Skeletal signs:** Periostitis (inflammation of the periosteum) and osteochondritis (e.g., Wimberger’s sign). The standard screening protocol involves non-treponemal tests like **VDRL or RPR**. Testing both the mother and the child is essential to correlate titers; a neonatal titer fourfold higher than the maternal titer is diagnostic. **2. Why Other Options are Incorrect:** * **Option B (PCR for TB):** While TB can cause osteomyelitis, it does not typically present with acute bullous lesions in neonates. * **Option C (HBsAg):** Hepatitis B in neonates is usually asymptomatic at birth and does not cause periostitis or bullous skin eruptions. * **Option D (ELISA):** While ELISA can be used for various infections (like HIV), VDRL remains the gold standard initial screening tool for syphilis due to its ability to monitor treatment response via titers. **Clinical Pearls for NEET-PG:** * **Snuffles:** Early-onset syphilitic rhinitis (highly infectious discharge). * **Wimberger’s Sign:** Focal erosion of the medial proximal tibial metaphysis. * **Hutchinson’s Triad (Late Syphilis):** Interstitial keratitis, sensorineural hearing loss, and Hutchinson teeth. * **Treatment of Choice:** Parenteral Penicillin G is the mainstay for both maternal and congenital syphilis.

Question 59: What is the most common cause of epiglottitis in children aged 5 years?

A. Haemophilus influenzae (Correct Answer)
B. Neisseria meningitidis
C. Streptococci
D. Pneumococci

Explanation: **Explanation:** **Haemophilus influenzae type b (Hib)** is the most common cause of acute epiglottitis in children. Although the incidence has significantly declined in regions with high vaccination coverage, it remains the leading pathogen globally, especially in unimmunized or partially immunized children. Epiglottitis is a life-threatening emergency characterized by rapid inflammation of the epiglottis, leading to potential airway obstruction. **Analysis of Options:** * **A. Haemophilus influenzae (Correct):** Historically and currently, Hib is the primary causative agent. It typically affects children between 2–7 years of age. * **B. Neisseria meningitidis:** While a cause of severe sepsis and meningitis, it is an extremely rare cause of epiglottitis. * **C. Streptococci:** Group A Streptococcus (S. pyogenes) and S. agalactiae are known causes, particularly in vaccinated populations where Hib incidence is low, but they are not the *most* common overall. * **D. Pneumococci:** Streptococcus pneumoniae can cause epiglottitis, but it ranks lower in frequency compared to Hib. **Clinical Pearls for NEET-PG:** * **Classic Presentation:** The "4 Ds"—**D**rooling, **D**ysphagia, **D**istress (respiratory), and **D**ysphonia (muffled "hot potato" voice). * **Positioning:** Children often assume the **"Tripod position"** (leaning forward on hands with neck extended) to maintain the airway. * **Radiology:** The lateral neck X-ray shows the **"Thumb sign"** (swollen epiglottis). * **Management:** The priority is **airway stabilization** (intubation) in a controlled environment (OR). Never examine the throat with a tongue depressor, as it may trigger fatal laryngospasm. * **Prophylaxis:** Rifampicin is given to close contacts of Hib cases.

Question 60: A patient presented with fever and coryza for the last 3 days, followed by a maculopapular erythematous rash that lasted for 48 hours and disappeared without leaving any pigmentation. This presentation is most commonly due to which of the following conditions?

A. Measles
B. Typhoid
C. Roseola infantum (Correct Answer)
D. Fifth disease

Explanation: ### Explanation The clinical presentation described is characteristic of **Roseola Infantum** (also known as Exanthema Subitum or Sixth Disease), typically caused by **Human Herpesvirus 6 (HHV-6)**. **Why Roseola Infantum is correct:** The hallmark of Roseola is a **high-grade fever** (often >39.5°C) lasting for 3–5 days, which **abruptly subsides** (defervescence). Immediately following the disappearance of the fever, a pale pink, maculopapular rash appears. Crucially, the rash is transient (lasting hours to 2 days) and fades **without leaving any pigmentation or desquamation**, matching the question's description perfectly. **Why the other options are incorrect:** * **Measles (Rubeola):** The rash in measles appears while the fever is at its peak (not after it subsides). It lasts for 6–7 days and characteristically disappears with **brownish staining (pigmentation)** and fine desquamation. * **Typhoid:** The "rose spots" of typhoid are sparse, blanching macules found on the trunk, usually appearing in the second week of illness, not following a 3-day prodrome of coryza. * **Fifth Disease (Erythema Infectiosum):** Caused by Parvovirus B19, it presents with a "slapped-cheek" appearance followed by a reticular, lace-like rash on the trunk and limbs. It does not follow the classic "fever ends, rash begins" pattern of Roseola. **High-Yield Clinical Pearls for NEET-PG:** * **Nagayama Spots:** Erythematous papules on the soft palate and uvula seen in Roseola. * **Febrile Seizures:** Roseola is one of the most common triggers for febrile seizures in infants due to the rapid rise in temperature. * **Age Group:** Most common between 6 months and 2 years of age. * **Sequence:** Fever → Defervescence → Rash (The "Suddenness" of the rash gives it the name *Exanthema Subitum*).

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Immunization Schedule

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Common Childhood Infections

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Pediatric HIV

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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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