Infectious Diseases Practice Questions

Q: Which of the following conditions does NOT typically present with a maculopapular rash?

Scarlet fever. The correct answer is **Scarlet fever** because it presents with a **sandpaper-like punctate erythematous rash**, rather than a classic maculopapular rash. ### 1. Why Scarlet Fever is the Correct Answer Scarlet fever, caused by Group A Streptococcus (GAS), is characterized by a **finely papular, "sandpaper" rash** on an erythematous base. It typically begins in the flexures (Pastia’s lines) and spreads to the trunk and extremities. Unlike maculopapular rashes, which consist of flat and raised spots, the rash in Scarlet fever is distinctively rough to the touch and is followed by desquamation. ### 2. Analysis of Incorrect Options * **Measles (Rubeola):** This is the prototype of a **maculopapular rash**. It typically begins behind the ears at the hairline and spreads cranio-caudally, becoming confluent. * **Exanthem Subitum (Roseola Infantum):** Caused by HHV-6, it presents with a high fever that subsides, followed by the sudden appearance of a **rose-pink maculopapular rash** starting on the trunk. * **Infectious Mononucleosis (EBV):** While not always present, a **maculopapular rash** frequently occurs in patients with IM, especially after the administration of aminopenicillins (Ampicillin/Amoxicillin). ### 3. High-Yield Clinical Pearls for NEET-PG * **Scarlet Fever Triad:** Strawberry tongue, circumoral pallor, and Pastia’s lines. * **Koplik Spots:** Pathognomonic for Measles (found on buccal mucosa opposite the lower 2nd molars). * **Forchheimer Spots:** Small petechiae on the soft palate seen in **Rubella** (German Measles). * **Nagayama Spots:** Erythematous papules on the soft palate/uvula seen in **Roseola**. * **Slapped Cheek Appearance:** Characteristic of Erythema Infectiosum (Fifth Disease/Parvovirus B19).

Q: Which of the following symptoms is NOT suggestive of Scarlet fever?

Nagayama spots. **Explanation:** **Nagayama spots** are the correct answer because they are characteristic of **Roseola Infantum (Exanthema Subitum)**, caused by Human Herpesvirus 6 (HHV-6), not Scarlet fever. These are small, erythematous papules or ulcers found on the soft palate and uvula. **Scarlet Fever** is caused by Group A Streptococcus (Streptococcus pyogenes) producing erythrogenic toxins. The other options are classic clinical features of this condition: * **Gooseflesh rash (Sandpaper rash):** This is the hallmark rash of Scarlet fever. It is a fine, erythematous, punctate rash that blanches on pressure and feels rough, similar to sandpaper or "gooseflesh." * **Strawberry tongue:** Initially, the tongue has a white coating with red papillae (White Strawberry Tongue); by day 4-5, the white coat sloughs off, leaving a bright red, inflamed surface (Red Strawberry Tongue). * **Desquamation:** As the rash fades, the skin undergoes "fine branny" desquamation, which is particularly prominent on the palms, soles, and tips of the fingers/toes. **Clinical Pearls for NEET-PG:** * **Pastia’s lines:** Linear petechiae in skin folds (axilla, antecubital fossa) seen in Scarlet fever. * **Circumoral pallor:** A pale area around the mouth contrasting with flushed cheeks. * **Treatment:** Penicillin is the drug of choice. * **Differential Diagnosis:** Nagayama spots = Roseola; Koplik spots = Measles; Forchheimer spots = Rubella.

Q: Which of the following statements regarding typhoid in children is false?

Relative bradycardia is invariably seen in children.. **Explanation:** Typhoid fever (Enteric fever), caused by *Salmonella Typhi*, presents differently in the pediatric population compared to adults. **Why Option D is the Correct Answer (False Statement):** Relative bradycardia (Faget’s sign) is a classic clinical sign of typhoid fever where the heart rate does not increase proportionally with the rise in body temperature. While this is a hallmark in adults, it is **not invariably seen in children**. In pediatric patients, especially younger children, tachycardia is a more common finding during the febrile phase. **Analysis of Other Options:** * **Option A (Splenomegaly):** This is a common clinical finding in typhoid fever, occurring due to the infiltration of the reticuloendothelial system by the bacteria. It usually appears by the end of the first week. * **Option B (Neutropenia):** Hematological changes in typhoid typically include leucopenia with a relative lymphocytosis. Neutropenia is a characteristic feature and helps differentiate it from pyogenic infections where neutrophilia is expected. * **Option C (Urine and Stool Culture):** The diagnostic yield of cultures changes over time. While blood cultures are most sensitive in the 1st week, stool and urine cultures become positive later, typically after the **2nd week** of illness as the bacteria are shed from the gallbladder and kidneys. **NEET-PG High-Yield Pearls:** * **Gold Standard Diagnosis:** Bone marrow culture (highest sensitivity, even after starting antibiotics). * **Most Common Culture:** Blood culture (positive in 90% of cases in the 1st week). * **Widal Test:** Significant only after the 1st week; look for a four-fold rise in titers. * **Drug of Choice:** Ceftriaxone (due to widespread multi-drug resistance/NALD strains). * **Complications:** Intestinal perforation and hemorrhage usually occur in the 3rd week.

Q: In rubella syndrome, all are seen except?

Macrophthalmos. **Explanation:** Congenital Rubella Syndrome (CRS) is characterized by a classic triad of **Cataracts, Cardiac defects (PDA), and Sensorineural deafness**. The correct answer is **Macrophthalmos** because CRS typically causes **Microphthalmos** (abnormally small eyes) due to the virus inhibiting cell division during ocular development. Macrophthalmos (large eyes) is characteristic of Congenital Glaucoma (Buphthalmos), which is a separate entity, though glaucoma can occasionally occur in CRS. **Analysis of Options:** * **Salt and Pepper Chorioretinopathy:** This is the **most common** ocular manifestation of CRS. It involves fine pigmentary changes in the retina that do not usually affect vision but are diagnostic. * **Congenital Cataract:** A hallmark of the "Gregg Triad." It is often bilateral and described as a "pearled" nuclear opacification. * **Cloudy Cornea:** This occurs in CRS due to either transient neonatal corneal edema or secondary to infantile glaucoma, which is a known (though less frequent) complication of the syndrome. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad (Gregg Triad):** Cataract, PDA (continuous machinery murmur), and Deafness. * **Skin Manifestation:** "Blueberry muffin" spots (extramedullary hematopoiesis). * **Radiology:** "Celery stalking" appearance of long bones (metaphyseal lucencies). * **Timing:** Risk is highest if the mother is infected during the **first trimester** (especially the first 8 weeks). * **Diagnosis:** Detection of Rubella-specific IgM in the neonate or persistence of IgG beyond 6 months.

Q: What management is indicated for an infant born to an HIV-positive mother?

Antiretroviral therapy (AZT). **Explanation:** The primary goal in managing an infant born to an HIV-positive mother is the prevention of parent-to-child transmission (PPTCT). **1. Why Option B is Correct:** Post-exposure prophylaxis (PEP) is mandatory for all HIV-exposed infants to reduce the risk of vertical transmission. According to current guidelines (NACO/WHO), **Zidovudine (AZT)** or Nevirapine (NVP) is initiated as soon as possible after birth (ideally within 6–12 hours) and continued for 6 to 12 weeks, depending on the risk stratification. **2. Why Other Options are Incorrect:** * **Option A & D:** In HIV-exposed infants, **BCG is NOT contraindicated** unless the infant is clinically symptomatic or confirmed to be HIV-positive with severe immunosuppression. In most endemic settings like India, BCG is administered at birth regardless of HIV exposure status. * **Option C:** Separation from the mother is contraindicated. Rooming-in is encouraged to promote bonding. Regarding feeding, exclusive breastfeeding for the first 6 months is recommended (provided the mother is on ART), or exclusive replacement feeding if it is "AFASS" (Affordable, Feasible, Acceptable, Sustainable, and Safe). Mixed feeding must be strictly avoided. **NEET-PG High-Yield Pearls:** * **Diagnosis:** The gold standard for diagnosing HIV in infants <18 months is **HIV DNA PCR** (at 6 weeks). Antibody tests (ELISA) are unreliable due to the persistence of maternal IgG antibodies. * **Prophylaxis:** **Cotrimoxazole prophylaxis** should be started at 6 weeks of age for all HIV-exposed infants to prevent *Pneumocystis jirovecii* pneumonia, continuing until the infant is confirmed HIV-negative. * **Confirmatory Test:** A definitive negative status is usually determined by antibody testing at **18 months**.

Q: A 4-year-old child presented with cough persisting for 1 month and low-grade fever. There was a history of contact with TB. What is the chest X-ray suggestive of?

Primary TB. ***Primary TB*** - A 4-year-old child with **TB contact** and persistent cough typically presents with **primary TB complex** (Ghon focus + hilar lymphadenopathy). - Primary TB in children characteristically shows **hilar lymphadenopathy** with or without parenchymal infiltrates, forming the **Ranke complex**. *Pleural effusion* - More commonly seen in **adolescents and adults** with post-primary TB, not typical in young children. - Would present with **decreased breath sounds** and **dullness to percussion**, which are not mentioned here. *Miliary TB* - Chest X-ray would show **diffuse tiny nodules** (2-3mm) throughout both lung fields, resembling millet seeds. - Represents **hematogenous dissemination** and typically presents with more severe systemic symptoms than described. *Cavitation* - A feature of **post-primary (adult-type) TB**, extremely rare in children under 10 years of age. - Occurs due to **caseous necrosis** and tissue breakdown, which is uncommon in primary TB due to immature immune response.

Q: In cases of Streptococcal pharyngitis, how early should treatment be initiated to effectively prevent Rheumatic fever?

9 days. ### Explanation **Correct Answer: C. 9 days** **The Medical Concept:** Acute Rheumatic Fever (ARF) is a delayed, non-suppurative sequela of Group A Beta-hemolytic Streptococcal (GABHS) pharyngitis. The primary goal of antibiotic therapy in streptococcal sore throat—beyond symptom relief and preventing transmission—is the prevention of ARF. Clinical studies have established a "grace period" for the initiation of antibiotics. To effectively prevent the autoimmune trigger that leads to Rheumatic Fever, GABHS must be eradicated from the pharynx within **9 days** of the onset of symptoms. **Analysis of Options:** * **A & B (7 and 8 days):** While initiating treatment earlier is clinically ideal for symptom control and reducing the spread of infection, these are not the "outer limit" defined by guidelines for ARF prevention. * **C (9 days):** This is the gold standard timeframe. Even if treatment is delayed up to 9 days after the sore throat begins, the risk of developing ARF is significantly neutralized. * **D (10 days):** Waiting until the 10th day or beyond significantly increases the risk of the immunological cascade that leads to ARF. Note: While the *duration* of oral Penicillin V treatment is 10 days, the *window* to start treatment is 9 days. **High-Yield Clinical Pearls for NEET-PG:** * **Primary Prevention:** Treating the initial pharyngitis within 9 days prevents the first attack of ARF. * **Secondary Prevention:** Once a patient has had ARF, they require long-term antibiotic prophylaxis (e.g., Benzathine Penicillin G every 3–4 weeks) to prevent recurrences. * **Post-Streptococcal Glomerulonephritis (PSGN):** Unlike Rheumatic Fever, early antibiotic treatment of GABHS pharyngitis **does not** reliably prevent the development of PSGN. * **Drug of Choice:** Oral Penicillin V for 10 days or a single intramuscular injection of Benzathine Penicillin G remains the treatment of choice.

Q: Which of the following investigations is the best method for diagnosing HIV in childhood?

P24 antigen. In pediatric HIV, the choice of diagnostic test depends primarily on the **age of the child**. This question addresses the challenge of diagnosing HIV in infants born to HIV-positive mothers. ### Why P24 Antigen is Correct In children under **18 months**, maternal IgG antibodies cross the placenta and can persist in the infant's circulation. Therefore, antibody-based tests (like ELISA) will yield false positives. To diagnose HIV in this age group, **Virological Tests** are required. * **DNA-PCR** is the gold standard (most sensitive). * **P24 Antigen** assay is a highly specific virological marker that detects the viral capsid protein. Among the given options, it is the only test that directly detects a component of the virus rather than the immune response, making it the "best" choice listed for early diagnosis. ### Why Other Options are Incorrect * **CD4 Cell Counts (A):** This is used for **staging** the disease and monitoring progression/response to ART, not for primary diagnosis. CD4 counts are naturally higher in infants than adults. * **ELISA (C) & Anti-HIV Antibody (D):** These are the screening tests of choice for adults and children **over 18 months**. In infants, they cannot distinguish between maternal antibodies and true neonatal infection. ### High-Yield Clinical Pearls for NEET-PG * **Gold Standard ( 18 months):** Antibody-based tests (ELISA followed by Western Blot/Rapid tests). * **Prophylaxis:** All HIV-exposed infants should receive **Nevirapine** (or Zidovudine) from birth and **Cotrimoxazole** (to prevent *Pneumocystis jirovecii*) starting at 6 weeks of age until infection is ruled out. * **Breastfeeding:** In India (NACO guidelines), exclusive breastfeeding is recommended for the first 6 months if replacement feeding is not "AFASS" (Affordable, Feasible, Acceptable, Sustainable, and Safe).

Q: The rash of chickenpox typically begins from which area of the body?

Face. ### Explanation **Correct Answer: D. Face** **Medical Concept:** Chickenpox, caused by the **Varicella-Zoster Virus (VZV)**, is characterized by a classic centripetal rash. The eruption typically begins on the **face** or the **trunk** and then spreads peripherally to the extremities. The hallmark of the chickenpox rash is its rapid progression from macules to papules, then to "dew-drop on a rose petal" vesicles, and finally crusting. A key diagnostic feature is **pleomorphism**, where lesions in all different stages of development are present simultaneously in the same anatomical area. **Analysis of Incorrect Options:** * **A & B (Leg and Hand):** These represent the distal extremities. In chickenpox, the rash is **centripetal**, meaning it is most dense on the trunk and face, sparing the distal extremities (palms and soles are rarely involved). In contrast, Smallpox presents with a **centrifugal** distribution, starting on the face/hands and involving the palms and soles. * **C (Genitalia):** While lesions can occasionally appear on mucous membranes (including the genital mucosa) as the disease progresses, it is never the primary site of onset. **High-Yield Clinical Pearls for NEET-PG:** * **Incubation Period:** 10–21 days (Average 14–16 days). * **Infectivity:** 1–2 days *before* the rash appears until all vesicles have crusted over. * **Secondary Attack Rate:** Very high (~90%). * **Tzanck Smear:** Shows **Multinucleated Giant Cells** with Cowdry Type A intranuclear inclusion bodies (also seen in HSV). * **Complications:** Secondary bacterial skin infections (most common in children) and Varicella pneumonia (most common/severe in adults). * **Congenital Varicella Syndrome:** Characterized by cicatricial skin scarring, limb hypoplasia, and chorioretinitis if the mother is infected in early pregnancy.

Q: A child presents with fever and unconsciousness for 1 day and pallor with no focal neurological deficit. What is the most probable diagnosis?

Cerebral malaria. ### Explanation The correct diagnosis is **Cerebral Malaria**. The clinical triad of **fever**, **altered sensorium (unconsciousness)**, and **pallor** is the classic presentation of severe *Plasmodium falciparum* malaria in children. The presence of pallor is a crucial diagnostic clue, indicating significant hemolysis or bone marrow suppression, which is characteristic of malaria but uncommon in isolated CNS infections. The absence of focal neurological deficits further supports this, as cerebral malaria typically presents with symmetrical encephalopathy. **Why other options are incorrect:** * **Viral Encephalitis:** While it presents with fever and altered sensorium, it is rarely associated with significant **pallor**. It often presents with more acute behavioral changes or seizures. * **Pyomeningitis (Acute Bacterial Meningitis):** This usually presents with high-grade fever, signs of meningeal irritation (Kernig’s/Brudzinski’s sign), and a bulging fontanelle in infants. Pallor is not a hallmark feature. * **Tubercular Meningitis (TBM):** TBM typically follows a **subacute/chronic course** (weeks, not 1 day). It often presents with cranial nerve palsies (focal deficits) and a prodromal phase of weight loss and low-grade fever. **Clinical Pearls for NEET-PG:** * **Definition:** Cerebral malaria is defined as unarousable coma (Glasgow Coma Scale 1 hour after a seizure, with *P. falciparum* parasitemia, after excluding other causes. * **Hypoglycemia:** Always check blood glucose in these patients, as it is a common complication of both severe malaria and quinine therapy. * **Drug of Choice:** According to current WHO and NVBDCP guidelines, **Intravenous Artesunate** is the treatment of choice for severe/cerebral malaria, regardless of the trimester of pregnancy or age. * **Retinopathy:** Funduscopic examination showing "malarial retinopathy" (whitening, vessel changes) is highly specific for cerebral malaria.

Question 1

Which of the following conditions does NOT typically present with a maculopapular rash?

Accepted Answer

Scarlet fever

Answer

Measles

Answer

Exanthem subitum

Answer

Infectious mononucleosis

Question 2

Which of the following symptoms is NOT suggestive of Scarlet fever?

Accepted Answer

Nagayama spots

Answer

Gooseflesh rash

Answer

Desquamation of palms

Answer

Strawberry tongue

Question 3

Which of the following statements regarding typhoid in children is false?

Accepted Answer

Relative bradycardia is invariably seen in children.

Answer

Splenomegaly may be seen.

Answer

Neutropenia may be present.

Answer

Urine and stool culture may show the organism after 2 weeks of illness.

Question 4

In rubella syndrome, all are seen except?

Accepted Answer

Macrophthalmos

Answer

Salt and paper chorioretinopathy

Answer

Congenital cataract

Answer

Cloudy cornea

Question 5

What management is indicated for an infant born to an HIV-positive mother?

Accepted Answer

Antiretroviral therapy (AZT)

Answer

BCG vaccine should not be given

Answer

Separation from the mother

Answer

All vaccinations except BCG should be administered

Question 6

A 4-year-old child presented with cough persisting for 1 month and low-grade fever. There was a history of contact with TB. What is the chest X-ray suggestive of?

Accepted Answer

Primary TB

Answer

Pleural effusion

Answer

Miliary TB

Answer

Cavitation

Question 7

In cases of Streptococcal pharyngitis, how early should treatment be initiated to effectively prevent Rheumatic fever?

Accepted Answer

9 days

Answer

7 days

Answer

8 days

Answer

10 days

Question 8

Which of the following investigations is the best method for diagnosing HIV in childhood?

Accepted Answer

P24 antigen

Answer

CD4 cell counts

Answer

ELISA

Answer

Anti-HIV antibody

Question 9

The rash of chickenpox typically begins from which area of the body?

Accepted Answer

Face

Answer

Leg

Answer

Hand

Answer

Genitalia

Question 10

A child presents with fever and unconsciousness for 1 day and pallor with no focal neurological deficit. What is the most probable diagnosis?

Accepted Answer

Cerebral malaria

Answer

Viral encephalitis

Answer

Pyomeningitis

Answer

Tubercular meningitis

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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