Infectious Diseases Practice Questions

Q: What is the most common presentation in congenital rubella syndrome?

Nerve deafness. **Explanation:** Congenital Rubella Syndrome (CRS) is caused by the transplacental transmission of the Rubella virus, primarily during the first trimester. While CRS is characterized by a classic triad (Cataracts, Cardiac defects, and Sensorineural hearing loss), it is essential to distinguish between the "most common" and "most specific" features for the NEET-PG exam. **Why Nerve Deafness is Correct:** **Sensorineural hearing loss (Nerve deafness)** is the **most common** clinical manifestation of CRS, occurring in approximately 60–80% of affected infants. It may be the sole manifestation of the infection, especially when the mother is infected after the 16th week of gestation. It can be unilateral or bilateral and is often not detected until later in infancy. **Analysis of Incorrect Options:** * **Salt and pepper retinopathy:** This is the **most common ocular finding** in CRS, but it is less frequent than hearing loss. It typically does not affect vision. * **Low birth weight:** While intrauterine growth restriction (IUGR) is a common non-specific feature of all TORCH infections, it is not the hallmark presentation of CRS. * **Patent ductus arteriosus (PDA):** This is the **most common cardiac defect** in CRS (followed by peripheral pulmonary artery stenosis), but cardiac issues occur in only about 50% of cases, making them less frequent than deafness. **Clinical Pearls for NEET-PG:** * **Classic Triad (Gregg’s Triad):** Cataracts, Sensorineural hearing loss, and PDA. * **Most Specific Sign:** "Blueberry muffin" spots (extramedullary hematopoiesis). * **Radiology:** "Celery stalking" appearance of long bones (metaphyseal lucencies). * **Timing:** The risk of fetal malformation is highest (up to 85%) if maternal infection occurs within the first 12 weeks of pregnancy.

Q: Which of the following statements regarding feeding of an HIV-infected child is true?

Exclusive top feeding. **Explanation:** The prevention of mother-to-child transmission (PMTCT) of HIV through breast milk is a critical aspect of pediatric HIV management. **Why "Exclusive Top Feeding" is the correct answer:** The primary goal in managing an infant born to an HIV-positive mother is to eliminate the risk of postnatal transmission. In clinical scenarios where **AFASS** criteria (Affordable, Feasible, Acceptable, Sustainable, and Safe) are met, **exclusive replacement feeding (top feeding)** is the preferred method as it completely eliminates the risk of HIV transmission via breast milk. **Analysis of Incorrect Options:** * **Options A & B (Breastfeeding for 4-6 months or 1 year):** Any duration of breastfeeding carries a cumulative risk of HIV transmission (approximately 5–20%). While WHO guidelines suggest exclusive breastfeeding for 6 months *if* replacement feeding is not safe (to avoid malnutrition and diarrhea), the question asks for the ideal "true" statement regarding feeding to prevent infection. Mixed feeding (combining breast milk and top feeds) is strictly contraindicated as it causes gut inflammation, significantly increasing the risk of HIV penetration. **High-Yield Clinical Pearls for NEET-PG:** 1. **AFASS Criteria:** Before advising top feeds, ensure the family can provide it safely. If AFASS is not met, exclusive breastfeeding with maternal ART is recommended. 2. **Never Mix Feed:** Mixed feeding has a higher transmission risk than exclusive breastfeeding. 3. **Prophylaxis:** Infants born to HIV-positive mothers should receive **Nevirapine (NVP)** prophylaxis for 6 weeks (extendable to 12 weeks in high-risk cases). 4. **Diagnosis:** The gold standard for diagnosing HIV in infants <18 months is **HIV DNA PCR** (at 6 weeks), not ELISA, due to the persistence of maternal antibodies.

Q: All of the following statements are true about Erythema infectiosum except:

This disease is also known as Roseola infantum.. **Explanation:** The correct answer is **B** because **Erythema infectiosum** (Fifth Disease) and **Roseola infantum** (Sixth Disease) are two distinct clinical entities caused by different viruses. 1. **Why Option B is the correct answer (False statement):** * **Erythema infectiosum** is caused by **Parvovirus B19**. * **Roseola infantum** (Exanthema subitum) is caused by **Human Herpesvirus 6 (HHV-6)** and occasionally HHV-7. Roseola is characterized by high fever for 3–5 days, followed by the sudden appearance of a rash *after* the fever subsides. 2. **Analysis of other options (True statements):** * **Option A:** Parvovirus B19 is indeed the causative agent. It is a single-stranded DNA virus that targets erythroid progenitor cells. * **Option C:** The rash of Erythema infectiosum typically follows a classic progression: it starts with an erythematous "slapped-cheek" appearance, followed by a **reticulate (lace-like) maculopapular rash** on the trunk and extremities. * **Option D:** In immunocompetent (healthy) individuals, the disease is usually mild and self-limiting. **High-Yield Clinical Pearls for NEET-PG:** * **Infectivity:** Patients are infectious *before* the onset of the rash. Once the rash appears, the child is no longer contagious. * **Aplastic Crisis:** Parvovirus B19 can cause a transient aplastic crisis in patients with high red cell turnover (e.g., Sickle Cell Anemia, Hereditary Spherocytosis). * **Pregnancy:** Infection in pregnancy can lead to **Hydrops fetalis** due to severe fetal anemia. * **Arthropathy:** In adults (especially females), Parvovirus B19 often presents with symmetrical small joint arthritis resembling Rheumatoid Arthritis.

Q: Hutchinson's triad is a classic sign of congenital syphilis. Which of the following is NOT a component of Hutchinson's triad?

Cataracts. **Explanation:** Hutchinson’s triad is a pathognomonic clinical finding associated with **Late Congenital Syphilis** (manifesting after 2 years of age). It represents the permanent sequelae of *Treponema pallidum* infection during fetal development. **Why Cataracts is the correct answer:** Cataracts are **not** a component of Hutchinson’s triad. While ocular involvement is common in congenital syphilis, it typically manifests as interstitial keratitis or chorioretinitis. Cataracts are more characteristically associated with **Congenital Rubella Syndrome** (along with sensorineural deafness and PDA). **Analysis of the Triad Components:** * **Interstitial Keratitis (Option A):** This is an inflammatory condition of the corneal stroma. It usually appears between ages 5 and 15, leading to corneal scarring and potential blindness if untreated. * **Notched Incisors (Option B):** Also known as **Hutchinson’s teeth**, these are permanent upper central incisors that are peg-shaped, widely spaced, and notched at the biting edge. * **Deafness (Option C):** This refers specifically to **Sensorineural hearing loss** caused by eighth cranial nerve (vestibulocochlear) involvement. It often develops suddenly around puberty. **High-Yield Clinical Pearls for NEET-PG:** * **Early Congenital Syphilis (<2 years):** Look for snuffles (persistent rhinitis), pemphigus syphiliticus (bullous rash on palms/soles), and Parrot’s pseudoparalysis (due to osteochondritis). * **Other Late Signs:** Mulberry molars (rudimentary cusps on first molars), Saber shins (anterior bowing of the tibia), and Saddle nose deformity. * **Screening:** VDRL/RPR are used for screening; FTA-ABS or TP-PA are confirmatory.

Q: What is the most common cause of death in measles patients?

Pneumonia. **Explanation:** **Pneumonia** is the most common cause of death associated with measles in children, accounting for approximately 60% of measles-related fatalities. Measles virus causes profound immunosuppression by depleting T-lymphocytes and suppressing the immune response for weeks to months. This predisposes patients to secondary bacterial infections (most commonly *S. pneumoniae*, *H. influenzae*, and *S. aureus*) or primary giant cell pneumonia (Hecht’s pneumonia) caused by the virus itself. **Analysis of Incorrect Options:** * **Encephalitis:** While Acute Disseminated Encephalomyelitis (ADEM) and Subacute Sclerosing Panencephalitis (SSPE) are severe neurological complications, they occur much less frequently than respiratory complications. * **Meningitis:** This is not a classic or common complication of measles. Neurological involvement typically presents as encephalitis rather than isolated meningitis. * **Dehydration:** While diarrhea is the most common *complication* of measles overall (especially in developing countries), it is secondary to pneumonia as a cause of mortality. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication:** Diarrhea. * **Most common cause of death:** Pneumonia. * **Most common CNS complication:** Febrile seizures. * **Most common cause of long-term neurological mortality:** SSPE (occurs 7–10 years after infection; characterized by high titers of measles antibody in CSF). * **Vitamin A supplementation:** Essential in all children with measles to reduce the severity of complications and mortality. * **Koplik spots:** Pathognomonic sign found on the buccal mucosa opposite the lower second molars during the pre-eruptive stage.

Q: All are features of Pertussis except –

Cerebellar Ataxia. **Explanation:** Pertussis (Whooping Cough), caused by *Bordetella pertussis*, is characterized by severe paroxysms of coughing. The complications of Pertussis are primarily divided into those caused by **increased intrathoracic/intra-abdominal pressure** and those caused by **toxin-mediated effects**. **Why Cerebellar Ataxia is the Correct Answer:** Cerebellar ataxia is **not** a recognized feature of Pertussis. While Pertussis can involve the central nervous system (CNS), it typically manifests as encephalopathy. Ataxia is more commonly associated with viral infections like Varicella (post-infectious cerebellitis). **Analysis of Other Options:** * **Encephalopathy (Option A):** This is a known severe neurologic complication. It is thought to be caused by hypoxia during coughing fits, cerebral edema, or toxin-mediated effects. It presents as seizures or altered consciousness. * **Subconjunctival Hemorrhage (Option B):** During the paroxysmal stage, the intense pressure generated by forceful coughing causes the rupture of small capillaries. This leads to subconjunctival hemorrhages, epistaxis, and petechiae on the face/neck. * **Bronchiectasis (Option D):** Chronic or severe Pertussis can lead to secondary bacterial pneumonia and localized airway destruction, eventually resulting in bronchiectasis as a long-term pulmonary complication. **High-Yield Clinical Pearls for NEET-PG:** * **Stages:** Catarrhal (most infectious), Paroxysmal (whooping cough), and Convalescent. * **Hematology:** Characterized by **absolute lymphocytosis** (due to Lymphocytosis Promoting Factor), which is a rare finding in bacterial infections. * **Drug of Choice:** Macrolides (Azithromycin is preferred in infants). * **Gold Standard Diagnosis:** Culture on **Regan-Lowe** or **Bordet-Gengou** medium. * **Post-exposure Prophylaxis:** Recommended for all household contacts regardless of vaccination status.

Q: What is the most important element in the treatment of diphtheria?

Antitoxin. **Explanation:** The primary pathology in diphtheria is caused by the potent **exotoxin** produced by *Corynebacterium diphtheriae*. This toxin inhibits protein synthesis, leading to local tissue necrosis (pseudomembrane formation) and systemic complications like myocarditis and neuritis. Once the toxin binds to host cell receptors, it becomes irreversible. Therefore, the **most important** and life-saving element of treatment is the **Diphtheria Antitoxin (DAT)**. DAT works by neutralizing the circulating (unbound) toxin in the bloodstream before it can enter the cells. **Why the other options are incorrect:** * **Antibiotics (Erythromycin and Penicillin):** While essential, they are **secondary** to antitoxin. Antibiotics serve to stop further toxin production by killing the bacteria, prevent the spread of the organism to others, and treat the carrier state. They do not neutralize the toxin already present in the system. **Erythromycin** is generally considered the drug of choice for eradication. * **Tetracycline:** This is not a first-line agent for diphtheria and is less effective than macrolides or penicillins. **High-Yield Clinical Pearls for NEET-PG:** * **Schick Test:** Used to determine the immune status of an individual toward diphtheria. * **Loffler’s Serum Slope/Tellurite Medium:** Specific culture media used for growth (colonies appear grey-black on Tellurite). * **Albert’s Stain:** Used to demonstrate metachromatic (volutin) granules. * **Treatment Priority:** In clinical practice, DAT should be administered as soon as a clinical diagnosis is made, without waiting for laboratory confirmation, as delay increases the risk of mortality.

Q: Hecht's pneumonia is a complication of which condition?

Measles. **Explanation:** **Hecht’s Pneumonia**, also known as **Giant Cell Interstitial Pneumonia**, is a severe and often fatal complication of **Measles (Rubeola)**. It typically occurs in immunocompromised children (e.g., those with leukemia or HIV) who fail to develop the characteristic measles rash due to impaired T-cell immunity. 1. **Why Measles is Correct:** The measles virus causes the fusion of infected cells, leading to the formation of **Warthin-Finkeldey giant cells** (multinucleated giant cells with eosinophilic intranuclear and intracytoplasmic inclusion bodies) in the lymphoid and pulmonary tissues. In Hecht’s pneumonia, these giant cells infiltrate the alveolar walls, leading to progressive respiratory failure. 2. **Why Other Options are Incorrect:** * **Mumps:** Primarily involves the parotid glands and testes; respiratory complications are rare and do not manifest as Hecht’s pneumonia. * **AIDS:** While patients with AIDS are at high risk for Hecht’s pneumonia if they contract measles, the pneumonia itself is specifically etiologically linked to the measles virus, not HIV. * **Mycoplasma:** Causes "Walking Pneumonia" characterized by interstitial infiltrates and cold agglutinins, but does not produce multinucleated giant cells. **High-Yield Clinical Pearls for NEET-PG:** * **Warthin-Finkeldey Cells:** Pathognomonic for Measles; found in nasal secretions, tonsils, and lung tissue. * **Koplik Spots:** The hallmark prodromal sign of measles (found opposite the lower second molars). * **Vitamin A:** Supplementation is recommended for all children with acute measles to reduce morbidity and mortality. * **SSPE (Subacute Sclerosing Panencephalitis):** A late neurological complication occurring years after a primary measles infection.

Question 1

Which of the following statements about herpangina is false?

Accepted Answer

May cause dysphagia.

Answer

May lead to high-grade fever.

Answer

May lead to vesicle formation in the anterior part of the mouth, numbering around 20-30.

Answer

The anterior portion of the mouth has only minor vesicles.

Question 2

Which of the following statements regarding feeding of HIV-infected children is/are true?

Accepted Answer

Breastfeeding for 6 months and then rapid weaning

Answer

Breastfeeding for 4–6 months then start weaning

Answer

Breastfeeding for 1 year then start weaning

Answer

Exclusive top feeding

Question 3

What is the most common presentation in congenital rubella syndrome?

Accepted Answer

Nerve deafness

Answer

Salt and pepper retinopathy

Answer

Low birth weight

Answer

Patent ductus arteriosus

Question 4

Which of the following statements regarding feeding of an HIV-infected child is true?

Accepted Answer

Exclusive top feeding

Answer

Breastfeeding for 4-6 months then starting weaning

Answer

Breastfeeding for 1 year then starting weaning

Answer

All of the above

Question 5

All of the following statements are true about Erythema infectiosum except:

Accepted Answer

This disease is also known as Roseola infantum.

Answer

The causative agent is Parvovirus B19.

Answer

A reticulate lacy exanthem may be noted on the trunk and extremities.

Answer

Clinical features are usually seen in healthy individuals.

Question 6

Hutchinson's triad is a classic sign of congenital syphilis. Which of the following is NOT a component of Hutchinson's triad?

Accepted Answer

Cataracts

Answer

Interstitial keratitis

Answer

Notched incisors

Answer

Deafness

Question 7

What is the most common cause of death in measles patients?

Accepted Answer

Pneumonia

Answer

Encephalitis

Answer

Meningitis

Answer

Dehydration

Question 8

All are features of Pertussis except –

Accepted Answer

Cerebellar Ataxia

Answer

Encephalopathy

Answer

Subconjunctival hemorrhage

Answer

Bronchiectasis

Question 9

What is the most important element in the treatment of diphtheria?

Accepted Answer

Antitoxin

Answer

Tetracycline

Answer

Erythromycin

Answer

Penicillin

Question 10

Hecht's pneumonia is a complication of which condition?

Accepted Answer

Measles

Answer

Mumps

Answer

AIDS

Answer

Mycoplasma

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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