Infectious Diseases Practice Questions

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.

Q: What is the most common complication of measles?

Otitis media. **Explanation:** Measles (Rubeola) is a highly contagious viral infection characterized by high fever, cough, coryza, conjunctivitis (the 3 Cs), and the pathognomonic Koplik spots. While the virus itself causes significant morbidity, its complications are frequent. **Why Otitis Media is the correct answer:** **Otitis media** is statistically the **most common complication** of measles, occurring in approximately 7–10% of cases. It occurs due to the virus causing inflammation of the respiratory mucosa and secondary bacterial invasion, leading to middle ear infection. For NEET-PG, it is crucial to distinguish between the "most common" and "most fatal" complication. **Analysis of Incorrect Options:** * **Orchitis (A):** This is a classic complication of **Mumps**, not Measles. It typically occurs in post-pubertal males. * **Pneumonia (B):** This is the **most common cause of death** (most fatal complication) associated with measles in children. It can be primary viral (Hecht’s giant cell pneumonia) or secondary bacterial. * **Seizures (D):** While febrile seizures can occur due to high fever in measles, they are not as frequent as otitis media. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication:** Otitis media. * **Most common cause of death:** Pneumonia. * **Most serious/delayed complication:** Subacute Sclerosing Panencephalitis (SSPE), occurring years after the initial infection. * **Vitamin A supplementation:** Essential in management as it reduces the severity of complications and mortality. * **Infectivity:** Maximum during the **pre-eruptive (prodromal) stage**. The patient is infectious from 4 days before to 4 days after the appearance of the rash.

Q: A 6-month-old child presents with recurrent seizures and poor development. The evaluation reveals hydrocephalus, impaired movement of the extremities, hypotonia, and retinal abnormalities. A computerized tomography (CT) scan demonstrates large ventricles and calcified lesions. Which of the following is the most likely diagnosis?

Toxoplasmosis. ### Explanation The clinical presentation of hydrocephalus, intracranial calcifications, and retinal abnormalities (chorioretinitis) forms the classic **Sabin Triad**, which is pathognomonic for **Congenital Toxoplasmosis**. **1. Why Toxoplasmosis is Correct:** Congenital Toxoplasmosis is caused by the transplacental transmission of *Toxoplasma gondii*. The CT findings of **diffuse intracranial calcifications** (scattered throughout the parenchyma) and ventriculomegaly (obstructive hydrocephalus due to aqueductal stenosis) are hallmark features. The "poor development" and "impaired movement" reflect the neurological sequelae of the infection, while "retinal abnormalities" typically refer to chorioretinitis, the most common ocular manifestation. **2. Why the Other Options are Incorrect:** * **Tay-Sachs Disease:** While it presents with developmental regression and hypotonia, it is characterized by a **cherry-red spot** on the macula and **macrocephaly** (due to GM2 ganglioside accumulation), not hydrocephalus or calcifications. * **Congenital Hydrocephalus:** This is a structural finding, not a primary diagnosis. It does not explain the intracranial calcifications or retinal abnormalities. * **Kernicterus:** This results from severe unconjugated hyperbilirubinemia. While it causes hypotonia (early) and movement disorders (choreoathetosis), it does not present with intracranial calcifications or hydrocephalus. **3. NEET-PG High-Yield Pearls:** * **Calcification Pattern:** In Toxoplasmosis, calcifications are **diffuse/scattered**; in Congenital CMV, they are typically **periventricular**. * **Classic Triad (Sabin Triad):** Hydrocephalus, Intracranial calcifications, and Chorioretinitis. * **Treatment:** The standard regimen is **Pyrimethamine, Sulfadiazine, and Folinic acid** for one year. * **Source:** Usually acquired via oocysts in cat feces or undercooked meat.

Q: Primary pneumococcal peritonitis in children is most commonly associated with which of the following conditions?

Cirrhosis. **Explanation:** **Primary Peritonitis** (also known as Spontaneous Bacterial Peritonitis or SBP) is an infection of the peritoneal fluid without an evident intra-abdominal source of perforation. **Why Cirrhosis is the Correct Answer:** In children, the most common underlying condition predisposing to primary peritonitis is **Nephrotic Syndrome**, followed closely by **Cirrhosis** (chronic liver disease). In patients with cirrhosis, the development of ascites provides a medium for bacterial growth. The underlying pathophysiology involves **impaired host defenses**, specifically decreased opsonic activity in the ascitic fluid and portosystemic shunting, which allows bacteria to bypass the hepatic reticuloendothelial system (Kupffer cells). While *Streptococcus pneumoniae* is the classic organism associated with primary peritonitis in Nephrotic Syndrome, it is also a major pathogen in cirrhotic patients, alongside Gram-negative organisms like *E. coli*. **Analysis of Incorrect Options:** * **B. Lymphoma:** While lymphoma causes immunosuppression, it is more commonly associated with opportunistic infections or secondary peritonitis due to bowel obstruction/perforation rather than primary pneumococcal peritonitis. * **C. Carcinoid tumors:** These are neuroendocrine tumors that do not typically predispose patients to spontaneous bacterial infections of the peritoneum. **NEET-PG High-Yield Pearls:** * **Most common organism overall:** *Streptococcus pneumoniae* is the most common cause of primary peritonitis in children (especially those with Nephrotic Syndrome). * **Clinical Presentation:** Sudden onset of fever, abdominal pain, and rebound tenderness in a child with pre-existing ascites. * **Diagnosis:** Established by paracentesis showing an **Absolute Neutrophil Count (ANC) >250 cells/mm³**. * **Treatment of choice:** Third-generation cephalosporins (e.g., Cefotaxime or Ceftriaxone).

Q: Which of the following statements about HIV in neonates is incorrect?

The transmission rate during pregnancy exceeds 90%.. **Explanation:** **1. Why Option C is the correct (incorrect statement):** The transmission rate of HIV from an untreated mother to her child is approximately **15% to 45%**, not >90%. With modern Prevention of Mother-to-Child Transmission (PMTCT) interventions—including Highly Active Antiretroviral Therapy (HAART), elective cesarean section, and avoidance of breastfeeding—this risk can be reduced to **less than 1–2%**. Therefore, the statement claiming a >90% transmission rate is factually incorrect. **2. Analysis of other options:** * **Option A:** Diagnosis in neonates is complex because maternal IgG antibodies cross the placenta and persist for up to 18 months. Therefore, standard ELISA/Western Blot cannot distinguish between infant infection and maternal antibodies. Diagnosis requires **HIV DNA or RNA PCR** (Nucleic Acid Testing). * **Option B:** Failure to thrive (FTT), persistent diarrhea, and recurrent infections (like oral candidiasis) are classic early clinical presentations of pediatric HIV. * **Option C:** Vertical transmission is the primary route of pediatric HIV, occurring in utero (transplacental), during delivery (birth canal), or postpartum (breastfeeding). **Clinical Pearls for NEET-PG:** * **Gold Standard Diagnosis:** HIV DNA PCR is the preferred test for infants <18 months. The first test is usually done within 4–6 weeks of birth. * **Prophylaxis:** All HIV-exposed infants should receive **Nevirapine** (or Zidovudine) prophylaxis immediately after birth for 6–12 weeks. * **Pneumocystis jirovecii (PJP) Prophylaxis:** Started at 6 weeks of age for all HIV-exposed infants until infection is ruled out. * **Breastfeeding:** In India (per NACO guidelines), exclusive breastfeeding is recommended for the first 6 months if replacement feeding is not "AFASS" (Affordable, Feasible, Acceptable, Sustainable, and Safe).

Q: A dome-shaped skull with a high forehead in an infant with slight hydrocephalus (Olympian brow) is characteristic of which condition?

Congenital syphilis. **Explanation:** The correct answer is **Congenital Syphilis**. The "Olympian brow" refers to a prominent, dome-shaped forehead caused by bony overgrowth (frontal bossing) due to chronic periostitis of the frontal and parietal bones. This is a classic late manifestation of congenital syphilis, often associated with other stigmata such as a saddle nose, Hutchinson’s teeth, and Mulberry molars. **Analysis of Options:** * **Marasmus:** While infants with severe malnutrition (Marasmus) may appear to have a large head relative to their wasted body ("monkey facies"), they do not exhibit true frontal bossing or the specific "Olympian brow" bony deformity. * **Rickets:** Rickets is a common cause of **frontal bossing** (caput quadratum), but the skull typically appears "boxy" or square-shaped rather than the specific "Olympian" dome-shape. Rickets is also characterized by craniotabes and a delayed closure of the anterior fontanelle. * **Arnold-Chiari Syndrome:** This involves structural defects in the cerebellum and brainstem. While it is frequently associated with hydrocephalus, it does not produce the specific "Olympian brow" bony configuration. **High-Yield Clinical Pearls for NEET-PG:** * **Hutchinson’s Triad:** Interstitial keratitis, Eighth nerve deafness, and Hutchinson’s teeth (notched incisors). * **Early Congenital Syphilis ( 2 years):** Clutton’s joints (painless knee effusion), Saber shins, and Higoumenakis sign (thickening of the medial end of the clavicle).

Question 1

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 2

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 3

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

Accepted Answer

Face

Answer

Leg

Answer

Hand

Answer

Genitalia

Question 4

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

Question 5

What is the most common complication of measles?

Accepted Answer

Otitis media

Answer

Orchitis

Answer

Pneumonia

Answer

Seizures

Question 6

A 6-month-old child presents with recurrent seizures and poor development. The evaluation reveals hydrocephalus, impaired movement of the extremities, hypotonia, and retinal abnormalities. A computerized tomography (CT) scan demonstrates large ventricles and calcified lesions. Which of the following is the most likely diagnosis?

Accepted Answer

Toxoplasmosis

Answer

Tay-Sachs disease

Answer

Congenital hydrocephalus

Answer

Kernicterus

Question 7

Primary pneumococcal peritonitis in children is most commonly associated with which of the following conditions?

Accepted Answer

Cirrhosis

Answer

Lymphoma

Answer

Carcinoid tumors

Answer

None of the above

Question 8

A 2-month-old infant presents for her first immunization. Physical examination reveals shivering and a body temperature of 39°C. The mother reports the infant is constantly crying, irritable, and refusing to feed. What is the most appropriate medical intervention in this case?

Accepted Answer

Delay immunization; return in 2-3 days

Answer

Administer immunization as per schedule

Answer

Administer immunizations one week apart

Answer

Postpone immunization for 6 months

Question 9

Which of the following statements about HIV in neonates is incorrect?

Accepted Answer

The transmission rate during pregnancy exceeds 90%.

Answer

Diagnosis cannot be accurately made by current methods.

Answer

Failure to thrive may be a presenting sign.

Answer

Vertical transmission from mother to child can occur.

Question 10

A dome-shaped skull with a high forehead in an infant with slight hydrocephalus (Olympian brow) is characteristic of which condition?

Accepted Answer

Congenital syphilis

Answer

Marasmus

Answer

Rickets

Answer

Arnold-Chiari syndrome

Infectious Diseases — MCQs

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