Infectious Diseases — MCQs

An 8-year-old child presents with a 3-day history of high-grade fever, vomiting, headache, and decreased responsiveness. Examination reveals a distressed child in shock, with maculopapular and ecchymotic rashes, bleeding from venipuncture sites, and hepatomegaly. Investigations show PCV = 65%, WBC = 4000, platelets = 25,000, and mildly prolonged PT. Chest X-ray reveals a left-sided pleural effusion. What is the most likely diagnosis?

Q166Easy

Congenital heart lesions associated with congenital rubella syndrome are:

Q167Medium

In a 7-month-old child diagnosed with Haemophilus influenzae meningitis, which of the following investigations should be done on follow-up?

Q168Easy

Which of the following is characteristic of the rash of measles?

Q169Easy

A patient presents with fever, cough, and headache. On the fourth day of illness, a rash develops. What is the probable diagnosis?

Q170Medium

A 6-year-old child is brought by his new foster mother who was concerned that when she brushed his teeth last night she noticed that his tongue was red in certain distinct patterns. He has otherwise not been ill. What is the most likely diagnosis?

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 161: What is the most common route of TB infection in a neonate born by cesarean section?

A. Hematogenous spread
B. Through skin contact
C. Inhalation of aerosol (Correct Answer)
D. Transplacental

Explanation: **Explanation:** The correct answer is **Inhalation of aerosol**. Congenital tuberculosis is rare, but when a neonate is born to a mother with active tuberculosis, the mode of transmission depends on the timing and environment. In the context of a **Cesarean section**, the risk of acquiring the infection during delivery (via aspiration of infected amniotic fluid or vaginal secretions) is bypassed. Therefore, the most common route for a neonate to acquire TB post-delivery is **postnatal transmission** through the inhalation of infected respiratory droplets (aerosols) from the mother or other close caregivers who have active pulmonary tuberculosis. **Analysis of Incorrect Options:** * **Hematogenous spread (A):** While this occurs in utero via the umbilical vein to the fetal liver (forming a primary complex in the liver), it is less common than postnatal aerosol transmission, especially if the mother’s primary site of infection is pulmonary. * **Through skin contact (B):** Tuberculosis is not transmitted through intact skin contact; it requires inhalation, ingestion, or direct inoculation into membranes. * **Transplacental (D):** This is the mechanism for true *congenital* TB (forming the primary complex in the liver). However, statistically, most neonates diagnosed with TB acquire it postnatally via the respiratory route rather than through the placenta. **High-Yield Clinical Pearls for NEET-PG:** * **Primary Site:** In congenital TB (transplacental), the primary complex is in the **liver**. In postnatal TB (inhalation), the primary complex is in the **lungs**. * **Cantwell’s Criteria:** Used to diagnose congenital TB; requires proven TB lesions plus one of the following: primary complex in the liver, skin lesions (papular), or exclusion of postnatal transmission. * **Management:** If a mother is diagnosed with active TB, the neonate should be screened. If asymptomatic, start **Isoniazid (INH) prophylaxis** for 6 months and delay BCG vaccination until prophylaxis is complete.

Question 162: Forschheimer spots are seen on which of the following locations?

A. Uvula (Correct Answer)
B. Trunk
C. Dorsal aspect of hand
D. Penis

Explanation: **Explanation:** **Forschheimer spots** are a classic clinical sign associated with **Rubella (German Measles)**. They are characterized by small, pinpoint, reddish-pink spots (petechiae) located on the **soft palate and uvula**. These spots appear during the prodromal phase or on the first day of the rash in approximately 20% of Rubella patients. While characteristic, they are not pathognomonic as they can occasionally be seen in Scarlet fever or Infectious Mononucleosis. **Analysis of Options:** * **A. Uvula (Correct):** This is the anatomical site for Forschheimer spots, specifically involving the soft palate and the uvula. * **B. Trunk:** While the Rubella rash (exanthem) typically starts on the face and spreads to the trunk, Forschheimer spots are an *enanthem* (mucosal rash) and are not found on the skin of the trunk. * **C. Dorsal aspect of hand:** This is not a site for specific enanthems. However, Gottron papules (seen in Dermatomyositis) are typically found on the dorsal aspect of interphalangeal joints. * **D. Penis:** This is not a site for Forschheimer spots. Genital lesions are more characteristic of STIs like Syphilis (Chancre) or HSV. **Clinical Pearls for NEET-PG:** * **Koplik Spots vs. Forschheimer Spots:** Koplik spots (Measles) are bluish-white spots on an erythematous base located on the buccal mucosa opposite the lower molars. Forschheimer spots (Rubella) are reddish petechiae on the soft palate/uvula. * **Rubella Triad (Congenital):** Cataract, Sensorineural hearing loss, and PDA (Patent Ductus Arteriosus). * **Rash Progression:** Rubella rash is known for its rapid spread and disappearance within 3 days ("3-day measles").

Question 163: A child on beta-2-agonist for treatment of bronchial asthma may exhibit all of the following features except?

A. Tremors
B. Hypoglycemia (Correct Answer)
C. Hypokalemia
D. Bronchodilation

Explanation: Beta-2 agonists (e.g., Salbutamol, Terbutaline) are the mainstay of treatment for bronchial asthma. Understanding their systemic side effects is high-yield for NEET-PG. ### **Explanation of the Correct Answer** **B. Hypoglycemia:** This is the correct answer because beta-2 agonists actually cause **hyperglycemia**, not hypoglycemia. Stimulation of beta-2 receptors in the liver and skeletal muscle promotes **glycogenolysis** (breakdown of glycogen to glucose) and **gluconeogenesis**. Additionally, they stimulate the release of glucagon, further raising blood glucose levels. ### **Analysis of Incorrect Options** * **A. Tremors:** This is the **most common side effect**. It occurs due to the direct stimulation of beta-2 receptors located in the skeletal muscles. * **C. Hypokalemia:** Beta-2 stimulation activates the **Na+/K+-ATPase pump**, causing an intracellular shift of potassium. This reduces serum potassium levels. (Note: This effect is utilized clinically to treat hyperkalemia). * **D. Bronchodilation:** This is the primary therapeutic goal. Stimulation of beta-2 receptors on bronchial smooth muscle increases cAMP, leading to muscle relaxation and airway widening. ### **NEET-PG High-Yield Pearls** * **Metabolic Effects:** Beta-2 agonists cause **Hyperglycemia, Hypokalemia, and Hypomagnesemia.** * **Cardiac Effects:** Even "selective" beta-2 agonists can cause **tachycardia** and palpitations due to reflex tachycardia (secondary to vasodilation) and minor stimulation of cardiac beta-1 receptors. * **Drug of Choice:** In acute asthma, inhaled Salbutamol is the drug of choice. * **Tolerance:** Prolonged use can lead to "downregulation" or tachyphylaxis of beta receptors.

Question 164: Dengue haemorrhagic fever (DHF) is suspected if all of the following are present EXCEPT?

A. Fever of over 10 days duration
B. Evidence of bleeding
C. Thrombocyte count less than 100,000/cmm
D. Evidence of lymphadenopathy (Correct Answer)

Explanation: **Explanation:** The diagnosis of **Dengue Haemorrhagic Fever (DHF)** is based on a specific constellation of clinical and laboratory findings defined by the WHO. The hallmark that distinguishes DHF from Dengue Fever (DF) is **plasma leakage**. **Why "Evidence of lymphadenopathy" is the correct answer:** While lymphadenopathy can occur in classical Dengue Fever (DF), it is **not** a diagnostic criterion for DHF. The WHO criteria for DHF require the presence of all four of the following: 1. **Fever:** Acute onset, high grade, and usually lasting **2 to 7 days**. 2. **Hemorrhagic manifestations:** Positive tourniquet test, petechiae, or mucosal bleeding. 3. **Thrombocytopenia:** Platelet count **< 100,000 cells/mm³**. 4. **Plasma Leakage:** Evidence of capillary leak (e.g., >20% rise in hematocrit, pleural effusion, or ascites). **Analysis of other options:** * **Option A (Fever duration):** While DHF fever typically lasts 2–7 days, the question asks for what is *not* a criterion. However, a fever lasting **over 10 days** is highly atypical for Dengue and usually suggests an alternative diagnosis (like Typhoid or Malaria). In the context of this specific MCQ, lymphadenopathy is the most "unrelated" clinical sign to the DHF diagnostic triad. * **Option B (Evidence of bleeding):** This is a core requirement for DHF (the "Hemorrhagic" component). * **Option C (Thrombocyte count < 100,000):** This is a mandatory laboratory criterion for DHF. **High-Yield Clinical Pearls for NEET-PG:** * **Critical Phase:** Occurs during defervescence (day 3–7). This is when plasma leakage and **Dengue Shock Syndrome (DSS)** typically develop. * **Best Indicator of Plasma Leakage:** Hemoconcentration (rising Hematocrit). * **Tourniquet Test:** Positive if ≥10–20 petechiae per square inch. * **Grading:** DHF is divided into 4 grades; Grades III and IV are classified as DSS.

Question 165: An 8-year-old child presents with a 3-day history of high-grade fever, vomiting, headache, and decreased responsiveness. Examination reveals a distressed child in shock, with maculopapular and ecchymotic rashes, bleeding from venipuncture sites, and hepatomegaly. Investigations show PCV = 65%, WBC = 4000, platelets = 25,000, and mildly prolonged PT. Chest X-ray reveals a left-sided pleural effusion. What is the most likely diagnosis?

A. Meningococcemia with DIC
B. Dengue hemorrhagic fever (Correct Answer)
C. Leptospirosis
D. Complicated malaria

Explanation: The correct answer is **Dengue Hemorrhagic Fever (DHF)**. ### **Why it is correct:** The clinical presentation and laboratory findings perfectly match the **WHO criteria for DHF**: 1. **High-grade fever** and constitutional symptoms. 2. **Hemorrhagic manifestations:** Ecchymotic rashes and bleeding from venipuncture sites. 3. **Thrombocytopenia:** Platelet count < 100,000/mm³ (here, 25,000). 4. **Evidence of Plasma Leakage (The Hallmark):** This is the most critical differentiator. The **PCV of 65%** (hemoconcentration > 20% from baseline) and the presence of **pleural effusion** and **hepatomegaly** confirm plasma leakage into the third space. ### **Why other options are incorrect:** * **Meningococcemia with DIC:** While it causes shock and purpura, it does not typically cause significant hemoconcentration (high PCV) or pleural effusion. WBC count is usually high (leukocytosis), whereas Dengue typically shows leukopenia. * **Leptospirosis:** Presents with conjunctival suffusion, jaundice, and renal failure. While it can cause bleeding (Weil’s disease), it does not explain the massive plasma leakage seen here. * **Complicated Malaria:** Can cause shock (Algid malaria) and thrombocytopenia, but the hallmark is severe anemia (low PCV), not hemoconcentration (high PCV). ### **NEET-PG High-Yield Pearls:** * **Dengue Grading:** DHF is graded I to IV. Grades III and IV (presence of shock) are termed **Dengue Shock Syndrome (DSS)**. * **Critical Phase:** Occurs during defervescence (day 3–7). This is when plasma leakage and shock are most likely to occur. * **Fluid Management:** Isotonic crystalloids (Ringer’s Lactate) are the gold standard for resuscitation. * **Diagnosis:** NS1 antigen (Day 1–5); IgM/IgG ELISA (after Day 5).

Question 166: Congenital heart lesions associated with congenital rubella syndrome are:

A. Ventricular Septal Defect (VSD) (Correct Answer)
B. Atrial Septal Defect (ASD)
C. Aortic Stenosis
D. Coarctation of the Aorta

Explanation: **Explanation:** Congenital Rubella Syndrome (CRS) occurs due to maternal infection with the Rubella virus during the first trimester of pregnancy. The virus is highly teratogenic and classically presents with the **Gregg’s Triad**: Cataracts, Sensorineural hearing loss, and Congenital Heart Disease (CHD). **Why VSD is the correct answer (in this context):** While the most characteristic cardiac lesion of CRS is **Patent Ductus Arteriosus (PDA)**, followed by **Peripheral Pulmonary Artery Stenosis (PPS)**, the question asks for associated lesions. Among the provided options, **Ventricular Septal Defect (VSD)** is a recognized cardiac association of CRS, although it is less common than PDA or PPS. In many standard medical examinations, if PDA is absent from the options, VSD is considered the next most likely associated defect. **Analysis of Incorrect Options:** * **B, C, and D:** While ASD, Aortic Stenosis, and Coarctation of the aorta are common congenital heart defects, they are not classically associated with the Rubella virus. Coarctation of the aorta is specifically linked to **Turner Syndrome**, while Aortic Stenosis is often associated with **Williams Syndrome**. **High-Yield Clinical Pearls for NEET-PG:** * **Most Common Cardiac Lesion:** Patent Ductus Arteriosus (PDA). * **Most Specific Cardiac Lesion:** Peripheral Pulmonary Artery Stenosis (PPS). * **Classic Triad (Gregg’s):** Cataract (Pearls white), Deafness (Sensorineural), and Heart defects (PDA). * **Other Features:** "Blueberry muffin" spots (extramedullary hematopoiesis), radiolucent bone lesions ("celery stalking"), and microcephaly. * **Risk Period:** Highest risk of malformation is if infection occurs within the first 8–12 weeks of gestation.

Question 167: In a 7-month-old child diagnosed with Haemophilus influenzae meningitis, which of the following investigations should be done on follow-up?

A. Brainstem Evoked Response Audiometry (BERA) (Correct Answer)
B. Contrast-Enhanced Computed Tomography (CECT) Scan
C. Magnetic Resonance Imaging (MRI)
D. X-ray Skull

Explanation: **Explanation:** **1. Why BERA is the Correct Answer:** Sensorineural hearing loss (SNHL) is the most common long-term complication of bacterial meningitis in children. *Haemophilus influenzae* type b (Hib) is particularly notorious for causing inflammatory damage to the cochlea (labyrinthitis ossificans). Since a 7-month-old infant cannot undergo conventional subjective audiometry, **Brainstem Evoked Response Audiometry (BERA)** is the gold standard objective investigation to assess hearing integrity. It should ideally be performed at the time of discharge or within 4 weeks of recovery to ensure early intervention and prevent speech delays. **2. Why Other Options are Incorrect:** * **CECT Scan (Option B):** CECT is not a routine follow-up investigation. It is indicated only if there is clinical suspicion of acute complications like subdural effusion, empyema, or brain abscess during the active phase of the disease. * **MRI (Option C):** While MRI is superior for visualizing soft tissue and inflammatory changes, it is not a routine screening tool for all meningitis survivors. It is reserved for specific neurological deficits or refractory cases. * **X-ray Skull (Option D):** This has no role in the management or follow-up of meningitis as it cannot visualize the brain parenchyma, meninges, or auditory pathways. **3. NEET-PG High-Yield Pearls:** * **Most common complication of bacterial meningitis:** Hearing loss (SNHL). * **Most common cause of meningitis in infants (post-neonatal):** *Streptococcus pneumoniae* (now more common than Hib due to vaccination). * **Steroid Role:** Dexamethasone (given 20 mins before or with the first dose of antibiotics) is specifically proven to reduce the incidence of hearing loss in *H. influenzae* meningitis. * **Follow-up Rule:** Every child post-meningitis must undergo a hearing assessment before discharge.

Question 168: Which of the following is characteristic of the rash of measles?

A. Begins as a maculopapular rash, then becomes vesicular
B. "Slapped cheek" appearance and lacy reticular pattern
C. Pustules on an erythematous base
D. Maculopapular eruption starting on upper trunk and spreading downward (Correct Answer)

Explanation: **Explanation:** Measles (Rubeola) is a highly contagious viral infection characterized by a specific prodrome and a classic exanthem. The correct answer is **D** because the measles rash is a **blanching maculopapular eruption** that typically begins 2–4 days after the onset of fever. It characteristically starts behind the ears and at the hairline (upper trunk/neck area) and spreads **cephalocaudally** (downward) to involve the trunk and extremities, including the palms and soles in severe cases. As the rash fades, it often leaves behind a brownish discoloration and fine desquamation. **Analysis of Incorrect Options:** * **Option A:** This describes the progression of **Varicella (Chickenpox)**, where lesions evolve from macules to papules, then to vesicles ("dewdrop on a rose petal"), and finally crusts. * **Option B:** This is the classic description of **Erythema Infectiosum (Fifth Disease)** caused by Parvovirus B19. * **Option C:** Pustules on an erythematous base are more characteristic of bacterial infections (like impetigo) or inflammatory conditions, not the viral exanthem of measles. **Clinical Pearls for NEET-PG:** * **Koplik Spots:** Small, bluish-white spots on the buccal mucosa opposite the lower molars; these are **pathognomonic** for measles and appear *before* the rash. * **The 3 C’s:** The prodromal phase is marked by **C**ough, **C**oryza, and **C**onjunctivitis. * **Vitamin A:** Supplementation is recommended for all children with acute measles to reduce morbidity and mortality. * **Complications:** The most common complication is Otitis Media; the most common cause of death is Pneumonia; the most dreaded late complication is **SSPE** (Subacute Sclerosing Panencephalitis).

Question 169: A patient presents with fever, cough, and headache. On the fourth day of illness, a rash develops. What is the probable diagnosis?

A. Measles (Correct Answer)
B. Mumps
C. Smallpox
D. Chickenpox

Explanation: **Explanation:** The clinical presentation of fever, cough, and headache followed by the appearance of a rash on the **fourth day** is a classic hallmark of **Measles (Rubeola)**. In Measles, the illness follows a predictable timeline: a 3-day prodromal phase characterized by the "3 Cs" (Cough, Coryza, and Conjunctivitis) and high-grade fever. The maculopapular rash typically appears on the **4th day**, starting behind the ears and spreading cephalocaudally (head to toe). **Why other options are incorrect:** * **Mumps:** Primarily presents with painful parotid swelling (parotitis). While fever and headache occur, a generalized maculopapular rash is not a standard clinical feature. * **Smallpox:** The rash typically appears on the **3rd day** of illness. Unlike measles, the rash is centrifugal (more dense on extremities) and progresses synchronously from papules to umbilicated vesicles and pustules. * **Chickenpox (Varicella):** The rash appears very early, usually on the **1st day** of fever. It is pleomorphic (all stages of rash—vesicles, papules, crusts—seen simultaneously) and has a centripetal distribution (more on the trunk). **High-Yield Clinical Pearls for NEET-PG:** * **Koplik Spots:** Pathognomonic for measles; small white spots on an erythematous base found on the buccal mucosa opposite the lower 2nd molars (appears 1–2 days before the rash). * **Vitamin A:** Supplementation is mandatory in measles management to reduce morbidity and mortality (especially blindness and pneumonia). * **Infectivity:** Patients are infectious from 4 days before to 4 days after the appearance of the rash. * **SSPE:** Subacute Sclerosing Panencephalitis is a rare, delayed neurological complication occurring years after the initial infection.

Question 170: A 6-year-old child is brought by his new foster mother who was concerned that when she brushed his teeth last night she noticed that his tongue was red in certain distinct patterns. He has otherwise not been ill. What is the most likely diagnosis?

A. Kawasaki disease
B. Pyogenic granuloma of the tongue
C. Geographic tongue (Correct Answer)
D. Hairy tongue

Explanation: **Explanation:** The correct diagnosis is **Geographic tongue** (Benign Migratory Glossitis). This condition is characterized by smooth, red, depapillated patches (loss of filiform papillae) surrounded by raised, grayish-white, serpentine borders. The "distinct patterns" mentioned in the question refer to the map-like appearance. Crucially, the lesions are dynamic—they heal in one area and migrate to another—and the patient is typically **asymptomatic** and otherwise healthy, as seen in this child. **Why the other options are incorrect:** * **Kawasaki disease:** While it presents with a "strawberry tongue," it is an acute systemic vasculitis. The child would be acutely ill with high-grade fever (≥5 days), conjunctivitis, rash, and lymphadenopathy. * **Pyogenic granuloma:** This is a solitary, vascular, pedunculated or sessile growth that often bleeds. it does not present as a "pattern" across the tongue. * **Hairy tongue:** This results from hypertrophy of filiform papillae, usually due to poor oral hygiene or tobacco use. It appears as a dark, furry discoloration (black or brown) on the dorsal surface, not red patches. **Clinical Pearls for NEET-PG:** * **Etiology:** Unknown, but associated with atopy, psoriasis, and stress. * **Histopathology:** Shows Munro’s microabscesses (neutrophils in the epithelium), similar to psoriasis. * **Management:** Reassurance is the mainstay as it is a benign, self-limiting condition. * **High-Yield Association:** Often seen in patients with a **fissured tongue**.

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Immunization Schedule

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Common Childhood Infections

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Respiratory Tract Infections

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Gastrointestinal Infections

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