Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 81: Risk of damage to the fetus by maternal rubella infection is maximum if the mother gets infected in which period of pregnancy?

A. 6-12 weeks (Correct Answer)
B. 20-24 weeks
C. 24-28 weeks
D. 32-36 weeks

Explanation: **Explanation:** The risk of fetal damage following maternal rubella infection is inversely proportional to the gestational age at the time of infection. This is due to the high rate of organogenesis occurring during the first trimester. **1. Why 6–12 weeks is correct:** During the first trimester (especially the first 12 weeks), the placental barrier is more permeable to the virus, and the developing fetal organs are at their most vulnerable stage. If infection occurs before 11–12 weeks of gestation, the risk of **Congenital Rubella Syndrome (CRS)** is as high as **80–90%**. Defects are often multiple (Gregg’s Triad) and severe. **2. Why the other options are incorrect:** * **20–24 weeks & 24–28 weeks:** By the second trimester, the risk of major structural malformations drops significantly. Between 16–20 weeks, the risk of damage (primarily sensorineural hearing loss) falls to about 10–15%. After 20 weeks, fetal damage is rare. * **32–36 weeks:** In the third trimester, while the rate of placental transmission increases again, the fetus is fully formed. Infection at this stage may lead to intrauterine growth restriction (IUGR) or neonatal infection, but not the classic structural malformations of CRS. **High-Yield Clinical Pearls for NEET-PG:** * **Gregg’s Triad:** Cataracts, Sensorineural deafness (most common), and Cardiac defects (PDA is most common; Peripheral Pulmonary Artery Stenosis is most specific). * **Classic Sign:** "Blueberry muffin" spots (extramedullary hematopoiesis). * **Diagnosis:** Detection of Rubella-specific IgM in the newborn or persistence of IgG beyond 6–12 months. * **Prevention:** Live attenuated **RA 27/3 vaccine**. It is contraindicated during pregnancy; women should avoid conception for 1 month after vaccination.

Question 82: In neonatal herpes, what is true?

A. Caused by HSV-II (Correct Answer)
B. Hepatosplenomegaly is diagnostic
C. Spontaneous recovery occurs
D. If not treated, it disseminates

Explanation: **Explanation:** Neonatal Herpes Simplex Virus (HSV) infection is a serious condition typically acquired during delivery through an infected birth canal. **1. Why Option A is Correct:** Approximately **70-80% of neonatal herpes cases are caused by HSV-2**. This is because HSV-2 is the primary cause of genital herpes in the mother. While HSV-1 cases are increasing due to changing practices, HSV-2 remains the classic and most common causative agent in the neonatal period. **2. Why the other options are Incorrect:** * **Option B:** While hepatosplenomegaly can occur in the disseminated form of the disease, it is **not diagnostic**. Diagnosis requires PCR of the blood/CSF or viral cultures from skin vesicles, as many other TORCH infections (like CMV or Syphilis) present with similar clinical findings. * **Option C:** Spontaneous recovery does **not** occur. Neonatal herpes is a medical emergency with high morbidity and mortality. Without treatment, the virus rapidly replicates and attacks the central nervous system or visceral organs. * **Option D:** This is a distractor. While the disease *can* disseminate, the question asks for what is "true" as a defining characteristic. Furthermore, even the localized "SEM" (Skin, Eye, Mouth) type requires immediate treatment to *prevent* dissemination; it doesn't mean it *always* disseminates if untreated—it may instead progress directly to encephalitis. **NEET-PG High-Yield Pearls:** * **Classification:** 1. SEM (Skin, Eye, Mouth), 2. CNS disease (Encephalitis), 3. Disseminated disease (highest mortality). * **Drug of Choice:** Intravenous **Acyclovir** (20 mg/kg every 8 hours for 14-21 days). * **Timing of Infection:** Most infections (85%) are **peripartum** (during delivery). * **Prevention:** If active genital lesions are present at the time of labor, a **Cesarean section** is indicated to reduce transmission risk.

Question 83: Ethambutol should be used very cautiously in childhood tuberculosis due to which of its side effects?

A. Ocular toxicity (Correct Answer)
B. Renal damage
C. Hepatotoxicity
D. Neurotoxicity

Explanation: **Explanation:** The correct answer is **A. Ocular toxicity**. Ethambutol is a bacteriostatic antitubercular drug that can cause **retrobulbar neuritis**, leading to decreased visual acuity, central scotomas, and loss of red-green color discrimination. In pediatric practice, Ethambutol is used cautiously because young children (typically those under 5–6 years old) are unable to reliably report visual changes or undergo formal ophthalmological testing (like Snellen charts or Ishihara plates). This makes early detection of toxicity difficult, potentially leading to irreversible vision loss. **Analysis of Incorrect Options:** * **B. Renal damage:** Ethambutol is primarily excreted by the kidneys, requiring dose adjustments in renal failure, but it is not inherently nephrotoxic. Aminoglycosides (like Streptomycin) are the primary ATT drugs associated with renal damage. * **C. Hepatotoxicity:** This is the most common side effect of the "big three" first-line drugs: **Isoniazid (INH), Rifampicin, and Pyrazinamide**. Ethambutol is notably non-hepatotoxic and is often continued when other drugs must be stopped due to drug-induced liver injury (DILI). * **D. Neurotoxicity:** While Ethambutol can rarely cause peripheral neuropathy, this is much more characteristic of **Isoniazid (INH)** due to interference with Pyridoxine (Vitamin B6) metabolism. **High-Yield Clinical Pearls for NEET-PG:** * **Monitoring:** Baseline and monthly visual acuity and color vision testing are mandatory for patients on Ethambutol. * **Dose-dependency:** Ocular toxicity is dose-related (more common at >25 mg/kg/day). * **Safe for Liver:** Ethambutol and Streptomycin are the preferred first-line agents in patients with pre-existing liver disease. * **NTEP Guidelines:** Under the National Tuberculosis Elimination Program (NTEP), Ethambutol is now included in the pediatric intensive phase regardless of age, provided monitoring is feasible.

Question 84: Epiglottitis is diagnosed in a 4-year-old unvaccinated child presenting at home. What is the appropriate management step?

A. Vaccination
B. Ampicillin for 4 days (Correct Answer)
C. Rifampin for 4 days
D. Doxycycline

Explanation: **Explanation:** **Core Concept:** Acute Epiglottitis is a life-threatening pediatric emergency, most commonly caused by *Haemophilus influenzae* type b (Hib). While the immediate priority in a hospital setting is airway management (intubation), the definitive medical treatment involves antibiotics. In the context of an unvaccinated child, the primary goal is to eradicate the pathogen. **Why Ampicillin is Correct:** Historically, **Ampicillin** was the drug of choice for *H. influenzae* infections before the widespread emergence of beta-lactamase-producing strains. In many standardized exam contexts (including older NEET-PG patterns), Ampicillin is listed as the classic treatment for Hib-related epiglottitis. It is administered parenterally to ensure rapid systemic coverage and clinical stabilization. **Analysis of Incorrect Options:** * **A. Vaccination:** While the Hib vaccine prevents the disease, it is a prophylactic measure, not a treatment for an acute, life-threatening infection. * **C. Rifampin for 4 days:** Rifampin is used for **chemoprophylaxis** of close contacts of a patient with Hib disease to eradicate nasopharyngeal carriage. It is not used to treat the active clinical disease itself. * **D. Doxycycline:** Tetracyclines are generally avoided in children under 8 years due to the risk of permanent tooth discoloration and are not the first-line treatment for Hib. **NEET-PG High-Yield Pearls:** * **Etiology:** *H. influenzae* type b (most common in unvaccinated); *Streptococcus pyogenes* (increasingly common in vaccinated populations). * **Clinical Signs:** The "4 Ds" – Drooling, Dysphagia, Dysphonia, and Distressed inspiratory efforts. * **X-ray Finding:** "Thumb sign" on lateral neck X-ray (swollen epiglottis). * **Management Rule:** Never examine the throat with a tongue depressor if epiglottitis is suspected, as it can trigger fatal laryngospasm. * **Modern Choice:** In current clinical practice, third-generation cephalosporins (e.g., Ceftriaxone) are preferred due to Ampicillin resistance.

Question 85: What is the most common complication of mumps?

A. Myocarditis
B. Orchitis (Correct Answer)
C. Uveitis
D. Conjunctivitis

Explanation: **Explanation:** Mumps is an acute viral illness caused by a **Paramyxovirus**, primarily characterized by painful swelling of the parotid glands. **Why Orchitis is the Correct Answer:** Epididymo-orchitis is the most common extra-salivary complication of mumps in post-pubertal males, occurring in approximately **20-30%** of cases. It typically presents with sudden onset of high fever, severe testicular pain, and swelling, usually 7–10 days after parotitis. While it can lead to testicular atrophy in about 50% of affected patients, permanent sterility is rare as the involvement is usually unilateral. **Analysis of Incorrect Options:** * **A. Myocarditis:** This is a rare and usually asymptomatic complication of mumps. While ECG changes (like depressed ST segments) can be seen, clinical heart failure is extremely uncommon. * **C. Uveitis & D. Conjunctivitis:** Ocular complications are not characteristic of mumps. Mumps is more likely to cause dacryoadenitis (inflammation of the lacrimal gland) rather than uveitis or conjunctivitis. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication in children:** Aseptic meningitis (usually benign and self-limiting). * **Most common cause of acquired sensorineural deafness in children:** Mumps (typically unilateral and permanent). * **Oophoritis:** Occurs in about 5% of post-pubertal females; it does not lead to infertility. * **Pancreatitis:** A well-known complication; mumps should be considered in a child with parotitis and epigastric pain. * **Diagnosis:** Primarily clinical; however, **Amylase** levels are elevated in both parotitis and pancreatitis.

Question 86: Which organ is most commonly involved in congenital tuberculosis?

A. Lungs
B. Liver (Correct Answer)
C. Lymph nodes
D. Skin

Explanation: **Explanation:** The correct answer is **Liver (Option B)**. This is a high-yield concept based on the unique fetal circulation. **Why the Liver is most commonly involved:** Congenital tuberculosis is primarily acquired via the **hematogenous route** through the umbilical vein. In fetal circulation, oxygenated and nutrient-rich blood (potentially carrying *Mycobacterium tuberculosis*) travels from the placenta via the **umbilical vein** directly to the liver. A significant portion of this blood enters the hepatic sinusoids before reaching the systemic circulation via the ductus venosus. Consequently, the liver acts as the first filter, leading to the frequent development of a **primary complex in the liver** (often associated with periportal lymphadenopathy). **Analysis of Incorrect Options:** * **Lungs (Option A):** While the lungs are the most common site for *postnatal* TB (acquired via inhalation), they are secondary in congenital TB. Lung involvement occurs only after the bacilli bypass the liver or are aspirated from infected amniotic fluid. * **Lymph Nodes (Option C):** While regional lymph nodes (especially periportal) are involved as part of the primary complex, the liver parenchyma itself is the primary site of seeding. * **Skin (Option D):** Cutaneous involvement (like tuberculosis cutis colliquativa) is rare in congenital presentations and usually signifies disseminated disease. **Clinical Pearls for NEET-PG:** * **Cantwell’s Criteria:** Used for diagnosing congenital TB; the presence of a primary hepatic complex is a definitive diagnostic feature. * **Route of Infection:** 1. Hematogenous (Umbilical vein → Liver); 2. Aspiration of infected amniotic fluid (Lungs). * **Presentation:** Usually appears in the 2nd or 3rd week of life with hepatosplenomegaly, respiratory distress, and fever. * **Key Distinction:** If the primary complex is in the **liver**, it is **congenital**; if it is in the **lung**, it is likely **postnatal** (unless aspiration is proven).

Question 87: An 8-year-old boy presented with a 4-day history of swelling on both sides of the face, below the ears. The swelling first started on the left side and then appeared on the right side 3 days later. What is the most likely diagnosis?

A. Bacterial sialadenitis
B. Sialadenosis
C. Epidemic parotitis (Correct Answer)
D. Sialadenitis

Explanation: **Explanation:** The clinical presentation of an 8-year-old child with acute, sequential, bilateral swelling of the parotid glands (below the ears) is classic for **Epidemic Parotitis**, commonly known as **Mumps**. **Why the correct answer is right:** Mumps is a viral infection caused by the *Rubulavirus* (Paramyxoviridae family). It typically affects children and is characterized by a prodrome of fever and malaise, followed by parotid swelling. A key diagnostic feature is the **asymmetrical progression**: it often starts on one side and involves the contralateral side within 2–3 days. The swelling displaces the earlobe upward and outward, which matches the description in the question. **Why incorrect options are wrong:** * **Bacterial Sialadenitis:** Usually presents as a **unilateral**, extremely painful, erythematous swelling. It is often associated with purulent discharge from Stensen’s duct and high-grade fever, unlike the typical viral course of Mumps. * **Sialadenosis:** This refers to non-inflammatory, non-neoplastic enlargement of the salivary glands, usually associated with systemic conditions like diabetes, alcoholism, or malnutrition. It is chronic and painless, not acute. * **Sialadenitis:** This is a general term for inflammation of the salivary gland. While Mumps is a form of viral sialadenitis, "Epidemic Parotitis" is the specific clinical diagnosis for this presentation in a pediatric population. **Clinical Pearls for NEET-PG:** * **Most common complication in children:** Aseptic meningitis. * **Most common complication in post-pubertal males:** Orchitis (usually unilateral; rarely leads to infertility). * **Diagnosis:** Primarily clinical; confirmed by IgM antibodies or PCR. * **Amylase:** Serum amylase levels are often elevated in Mumps due to salivary gland involvement. * **Prevention:** Live attenuated vaccine (MMR/MMRV).

Question 88: Which is a common complication of mumps in children?

A. Aseptic meningitis (Correct Answer)
B. Pancreatitis
C. Pneumonia
D. Encephalitis

Explanation: **Explanation:** Mumps is an acute viral infection caused by the **Rubulavirus** (Paramyxoviridae family). While parotitis is the hallmark clinical feature, the virus is highly neurotropic, making involvement of the central nervous system (CNS) very common. **1. Why Aseptic Meningitis is correct:** Aseptic meningitis is the **most common extra-salivary complication** of mumps in children. It occurs in up to 10% of clinical cases, though CSF pleocytosis (increased white cells) is found in nearly 50% of patients even without meningeal symptoms. It is typically benign, characterized by headache, fever, and neck stiffness, and carries a much better prognosis than other viral meningitides. **2. Analysis of Incorrect Options:** * **B. Pancreatitis:** While a classic complication, it is less common than meningitis in the pediatric population. It presents with epigastric pain and elevated serum amylase (though amylase is also elevated in parotitis). * **C. Pneumonia:** This is not a standard complication of mumps. Respiratory involvement is more characteristic of Measles or RSV. * **D. Encephalitis:** Mumps encephalitis is a rare (1 in 6,000 cases) but severe complication. It involves parenchymal damage and carries a higher risk of permanent sequelae compared to the more common aseptic meningitis. **Clinical Pearls for NEET-PG:** * **Orchitis:** The most common complication in **post-pubertal males** (up to 30%), usually unilateral; rarely leads to absolute sterility. * **Oophoritis:** Occurs in ~7% of post-pubertal females. * **Deafness:** Mumps is a classic cause of sudden, usually unilateral, **sensorineural hearing loss**. * **Diagnosis:** Most commonly clinical; IgM ELISA is the gold standard for serology. * **Prevention:** Live attenuated vaccine (Jeryl Lynn strain) as part of MMR.

Question 89: What is the most common cause of acute epiglottitis in children?

A. Haemophilus influenzae
B. Pseudomonas species
C. Streptococcus pyogenes (Correct Answer)
D. Staphylococcus aureus

Explanation: **Explanation:** **1. Why Streptococcus pyogenes is the correct answer:** Historically, *Haemophilus influenzae* type b (Hib) was the leading cause of acute epiglottitis. However, following the widespread implementation of the **Hib conjugate vaccine**, the incidence of epiglottitis caused by *H. influenzae* has plummeted by over 90%. In the post-vaccination era, **Group A Beta-hemolytic Streptococcus (*Streptococcus pyogenes*)** has emerged as the most common bacterial pathogen isolated from children with this condition. Other common pathogens now include *Streptococcus pneumoniae* and *Staphylococcus aureus*. **2. Why the other options are incorrect:** * **Haemophilus influenzae (Option A):** While it remains a potent cause in unimmunized children or vaccine-failure cases, it is no longer the "most common" cause in populations with high vaccine coverage. * **Pseudomonas species (Option B):** This is an opportunistic gram-negative organism. It is an extremely rare cause of epiglottitis and is typically only seen in severely immunocompromised patients. * **Staphylococcus aureus (Option D):** While *S. aureus* (including MRSA) is an increasing cause of supraglottic infections and bacterial tracheitis, it currently ranks behind *Streptococcus* species in frequency for acute epiglottitis. **3. Clinical Pearls for NEET-PG:** * **Clinical Triad:** The "3 Ds"—**D**rooling, **D**ysphagia, and **D**istress (Stridor). * **Classic Sign:** Patients often assume the **"Tripod position"** (leaning forward on outstretched arms) to maintain the airway. * **X-ray Finding:** Lateral neck X-ray shows the **"Thumb sign"** (swollen epiglottis). * **Management:** This is a medical emergency. **Do not examine the throat** with a tongue depressor as it may trigger fatal laryngospasm. The priority is airway stabilization in the OR.

Question 90: Which of the following is the most common cause of tonsillitis in children?

A. Follicular
B. Atrophic
C. Hypertrophic
D. Parenchymatous (Correct Answer)

Explanation: **Explanation:** Acute tonsillitis is a common pediatric infection involving the inflammation of the palatine tonsils. It is clinically classified into four types based on the extent and location of the inflammation. **1. Why Parenchymatous is Correct:** **Acute Parenchymatous Tonsillitis** is the most common form. In this type, the **entire substance (parenchyma) of the tonsil** is uniformly affected. The tonsils appear symmetrically enlarged, congested, and bright red. Because the inflammation involves the whole lymphoid tissue rather than just the surface or the crypts, it is the most frequent presentation seen in clinical practice. **2. Analysis of Incorrect Options:** * **Follicular Tonsillitis:** This occurs when the infection spreads from the crypts, and the purulent material presents as yellowish spots on the tonsillar surface. It is a progression of catarrhal tonsillitis but is less common than the generalized parenchymatous form. * **Hypertrophic Tonsillitis:** This is generally a feature of **chronic tonsillitis**, where permanent enlargement occurs due to repeated infections, rather than an acute inflammatory stage. * **Atrophic Tonsillitis:** This is also a form of chronic tonsillitis where the tonsils become small and fibrotic. It is rare in children and more common in adults. **Clinical Pearls for NEET-PG:** * **Most common causative organism:** Group A Beta-hemolytic Streptococcus (GABHS/ *S. pyogenes*). * **Complication to watch:** Peritonsillar abscess (Quinsy) is a common localized complication. * **Jones Criteria:** Always screen for Rheumatic Fever if GABHS tonsillitis is suspected. * **Membranous Tonsillitis D/D:** Must be differentiated from Diphtheria (greyish-white membrane that bleeds on touch) and Infectious Mononucleosis.

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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