Infectious Diseases — MCQs

A 5-year-old girl presents to the Emergency Department with sudden onset of difficulty in breathing, fever, and pruritus. She has no past history of lung infection or recent travel, but has a history of pica. On examination, wheezing and hepatomegaly are present. Peripheral smear shows marked eosinophilia and leukocytosis. What is the best test to aid in the diagnosis?

Q35Medium

Which of the following infections typically manifests initially as an infection of the limbic regions of the brain in children?

Q36Easy

Which of the following is NOT a neurological complication of rubeola?

Q37Easy

Which is not a major component of rheumatic fever?

Q38Medium

What is the characteristic feature of early congenital syphilis?

Q39Easy

The term infantile polyarteritis nodosa was formerly used for which condition?

Q40Easy

Which of the following is NOT associated with Kawasaki disease?

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 31: Which infection is most likely associated with this type of eye problem in children?

A. Typhoid
B. Rubella (Correct Answer)
C. HIV
D. Measles

Explanation: The correct answer is **Rubella**, specifically in the context of **Congenital Rubella Syndrome (CRS)**. ### **Explanation of the Correct Answer** Rubella is a classic cause of congenital eye defects. When a mother is infected during the first trimester, the virus interferes with organogenesis. The most characteristic eye finding is a **"Pearlescent" Nuclear Cataract** (often bilateral). Other ocular manifestations include **"Salt and Pepper" Retinopathy** (the most common ocular finding), microphthalmos, and infantile glaucoma. The classic Gregg’s Triad for CRS includes: 1. **Cataracts** (Eye) 2. **Sensorineural Hearing Loss** (Ear - Most common overall) 3. **Congenital Heart Disease** (Heart - Patent Ductus Arteriosus or Peripheral Pulmonary Artery Stenosis) ### **Why Other Options are Incorrect** * **Typhoid:** Primarily a systemic gastrointestinal illness. While it can cause "Rose spots" on the trunk, it does not typically cause congenital or acute pediatric eye malformations. * **HIV:** Pediatric HIV usually presents with opportunistic infections, failure to thrive, or lymphadenopathy. While CMV retinitis can occur in advanced stages, it is not a primary association for structural eye defects in children. * **Measles:** While Measles is famous for **Koplik spots** and can cause severe **keratitis** leading to blindness (especially in Vitamin A deficient children), it does not cause the congenital structural defects (like cataracts) associated with Rubella. ### **High-Yield Clinical Pearls for NEET-PG** * **Most common finding in CRS:** Sensorineural deafness. * **Most common ocular finding in CRS:** Salt and Pepper Retinopathy (does not significantly affect vision). * **Most specific ocular finding:** Pearlescent nuclear cataract. * **Dermal Erythropoiesis:** Leads to the "Blueberry Muffin" rash (also seen in CMV). * **Diagnosis:** Confirmed by Rubella-specific IgM in the newborn or persistent IgG levels beyond 6 months.

Question 32: In a child immunized for hepatitis B, which marker indicates seroconversion?

A. HBs Ag
B. Anti HBc IgM
C. Anti HBs (Correct Answer)
D. Anti HBc IgG

Explanation: ### Explanation **Correct Answer: C. Anti HBs** **1. Why Anti-HBs is the Correct Answer:** The Hepatitis B vaccine contains only the **Hepatitis B surface Antigen (HBsAg)**, which is a recombinant protein. When a child is immunized, their immune system recognizes this surface protein and produces specific antibodies against it, known as **Anti-HBs (Hepatitis B surface antibody)**. * **Seroconversion** is defined by the appearance of these antibodies in the serum. * A protective level is generally considered to be **≥10 mIU/mL**. * Since the vaccine does not contain the viral core or the whole virus, the body *only* produces antibodies against the surface component. **2. Why the Other Options are Incorrect:** * **A. HBsAg:** This is the actual viral surface antigen. Its presence in the blood indicates an **active infection** (acute or chronic), not immunity from vaccination. * **B. Anti-HBc IgM:** These are antibodies against the Hepatitis B **core** antigen. They appear during **acute infection** or a flare-up of chronic infection. Because the vaccine lacks the core antigen, these antibodies are never produced by vaccination. * **D. Anti-HBc IgG:** These indicate a **past or chronic infection**. Like IgM, these are directed against the core antigen. Their absence in a person with positive Anti-HBs confirms that the immunity is due to **vaccination** rather than a prior natural infection. **3. NEET-PG High-Yield Pearls:** * **Vaccine-induced immunity:** Anti-HBs (+), Anti-HBc (-), HBsAg (-). * **Natural infection immunity:** Anti-HBs (+), Anti-HBc (+) [IgG], HBsAg (-). * **Window Period:** Both HBsAg and Anti-HBs are negative; **Anti-HBc IgM** is the only marker present. * **Chronic Infection:** HBsAg persists for >6 months. * **Hepatitis B Vaccine Schedule:** 0, 1, and 6 months (standard) or 6, 10, 14 weeks (under National Immunization Schedule in India).

Question 33: A line of conjunctival inflammation on the lower eyelid margin is diagnostic of which condition?

A. Measles (Correct Answer)
B. Rubella
C. Kawasaki disease
D. Infectious mononucleosis

Explanation: **Explanation:** The correct answer is **Measles (Rubeola)**. The specific clinical sign described is known as **Stimson’s line**. It is a transverse line of conjunctival inflammation/hyperemia appearing along the margin of the lower eyelid during the prodromal phase of Measles. **Why Measles is correct:** Measles is characterized by a distinct prodromal phase consisting of the "3 Cs": **C**ough, **C**oryza, and **C**onjunctivitis. Stimson’s line is one of the earliest signs of the disease, appearing even before the pathognomonic **Koplik spots** (found on the buccal mucosa opposite the lower second molars). **Why other options are incorrect:** * **Rubella (German Measles):** While it presents with a rash and lymphadenopathy (retroauricular/suboccipital), it typically features **Forchheimer spots** (petechiae on the soft palate) rather than Stimson’s line. * **Kawasaki Disease:** This condition presents with **bilateral non-exudative conjunctival injection** (sparing the limbus), but it does not manifest as a specific line on the lower eyelid margin. * **Infectious Mononucleosis:** This is associated with exudative pharyngitis, lymphadenopathy, and hepatosplenomegaly. A common ocular finding is **Hoagland sign** (early transient bilateral upper eyelid edema), not Stimson’s line. **High-Yield Clinical Pearls for NEET-PG:** * **Stimson’s Line:** Earliest ocular sign of Measles. * **Koplik Spots:** Pathognomonic for Measles; appear 48 hours before the rash. * **Vitamin A:** Supplementation is mandatory in Measles management to prevent complications like blindness and pneumonia. * **Order of disappearance:** Koplik spots disappear as the maculopapular rash appears (which spreads in a cephalocaudal direction).

Question 34: A 5-year-old girl presents to the Emergency Department with sudden onset of difficulty in breathing, fever, and pruritus. She has no past history of lung infection or recent travel, but has a history of pica. On examination, wheezing and hepatomegaly are present. Peripheral smear shows marked eosinophilia and leukocytosis. What is the best test to aid in the diagnosis?

A. Tuberculin skin test
B. ELISA for Toxocara (Correct Answer)
C. Histoplasmin test
D. Silver stain of gastric aspirate

Explanation: **Explanation:** The clinical presentation of fever, wheezing (mimicking asthma), hepatomegaly, and marked peripheral eosinophilia in a child with a history of **pica** is classic for **Visceral Larva Migrans (VLM)**, caused by the migration of *Toxocara canis* or *Toxocara cati* larvae through human tissues. **Why ELISA for Toxocara is correct:** Humans (accidental hosts) ingest eggs from soil contaminated with dog or cat feces. The larvae hatch in the intestine and migrate to the liver and lungs, but cannot complete their life cycle, leading to an intense inflammatory response. Since the larvae do not mature into adults in humans, **stool examination for eggs is always negative**. Therefore, the diagnosis relies on serology. **ELISA for Toxocara excretory-secretory (TES) antigens** is the gold standard for diagnosis due to its high sensitivity and specificity. **Why other options are incorrect:** * **Tuberculin skin test:** Used for Tuberculosis. While TB can cause fever and lung findings, it does not typically present with sudden wheezing, pica, and profound eosinophilia. * **Histoplasmin test:** Used for Histoplasmosis (fungal infection). It is rarely used for acute diagnosis and does not explain the eosinophilic response seen here. * **Silver stain of gastric aspirate:** Used to identify *Pneumocystis jirovecii* or *Mycobacterium tuberculosis*. It has no role in diagnosing Toxocariasis. **NEET-PG High-Yield Pearls:** * **Classic Triad of VLM:** Hepatomegaly, marked eosinophilia, and hypergammaglobulinemia. * **Ocular Larva Migrans (OLM):** A variant where larvae migrate to the eye, often presenting as a retinal granuloma mimicking retinoblastoma. * **Treatment:** Albendazole is the drug of choice; corticosteroids are added if there is severe pulmonary or ocular involvement to reduce inflammation.

Question 35: Which of the following infections typically manifests initially as an infection of the limbic regions of the brain in children?

A. Enterovirus
B. Rabies (Correct Answer)
C. Epstein-Barr virus
D. Cytomegalovirus

Explanation: **Explanation:** The correct answer is **Rabies**. **Why Rabies is Correct:** Rabies virus is a neurotropic rhabdovirus that travels via retrograde axonal transport from the site of inoculation to the central nervous system. A hallmark of its early pathogenesis is its predilection for the **limbic system** (including the hippocampus, amygdala, and hypothalamus). This specific localization explains the classic clinical presentation of "furious rabies," characterized by emotional lability, agitation, aggression, and hydrophobia, as the limbic system governs emotions and behavior. Histologically, this is often associated with **Negri bodies**, most commonly found in the pyramidal cells of the hippocampus and Purkinje cells of the cerebellum. **Why Other Options are Incorrect:** * **Enterovirus:** Typically causes aseptic meningitis or encephalitis with a predilection for the brainstem (especially Enterovirus 71) or anterior horn cells of the spinal cord (Polio), rather than the limbic system. * **Epstein-Barr Virus (EBV):** While it can cause encephalitis, it usually presents as a diffuse process or involves the basal ganglia and thalamus; it is not specifically known for initial limbic involvement. * **Cytomegalovirus (CMV):** In neonates, it typically causes periventricular calcifications. In immunocompromised children, it causes a subacute diffuse encephalitis or ventriculoencephalitis. **NEET-PG High-Yield Pearls:** * **Limbic Predilection:** While Rabies involves the limbic system, **Herpes Simplex Encephalitis (HSE)** is the most common cause of sporadic fatal encephalitis involving the temporal lobes/limbic system. However, among the options provided, Rabies is the classic answer for limbic behavioral changes. * **Incubation Period:** Usually 1–3 months; depends on the distance of the bite from the CNS. * **Diagnosis:** Post-mortem identification of Negri bodies or ante-mortem skin biopsy from the nape of the neck (nuchal skin) for viral antigen.

Question 36: Which of the following is NOT a neurological complication of rubeola?

A. Subacute sclerosing panencephalitis (SSPE)
B. Encephalitis
C. Transverse myelitis
D. Peripheral neuropathy (Correct Answer)

Explanation: **Explanation:** Rubeola (Measles) is a highly contagious viral infection known for its significant neurotropism. While it primarily affects the respiratory system, it can cause various central nervous system (CNS) complications. **Why Peripheral Neuropathy is the correct answer:** Peripheral neuropathy is **not** a recognized complication of rubeola. Measles complications typically involve the CNS (brain and spinal cord) rather than the peripheral nerves. Conditions like Guillain-Barré Syndrome (a peripheral nerve issue) are more commonly associated with viruses like Campylobacter jejuni, CMV, or Zika, but not classically with Measles. **Analysis of Incorrect Options:** * **Subacute Sclerosing Panencephalitis (SSPE):** A rare, fatal, late complication occurring 7–10 years after infection. It is caused by a persistent mutant measles virus and is characterized by cognitive decline, myoclonic jerks, and periodic complexes on EEG. * **Encephalitis:** This can occur in two forms: **Acute Disseminated Encephalomyelitis (ADEM)**, an immune-mediated demyelinating disease occurring 1–2 weeks after the rash, and **Measles Inclusion Body Encephalitis (MIBE)**, which occurs in immunocompromised individuals. * **Transverse Myelitis:** Though rare, measles can trigger an inflammatory response in the spinal cord, leading to acute transverse myelitis. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication of Measles:** Otitis media. * **Most common cause of death in Measles:** Pneumonia (Hecht’s giant cell pneumonia). * **SSPE Marker:** Elevated anti-measles antibody titers in the CSF and serum. * **Vitamin A:** Supplementation reduces morbidity and mortality in all children with acute measles.

Question 37: Which is not a major component of rheumatic fever?

A. carditis
B. polyarthritis
C. subcutaneous nodules
D. arthralgia (Correct Answer)

Explanation: The diagnosis of Acute Rheumatic Fever (ARF) is based on the **Revised Jones Criteria (2015)**. This system categorizes clinical and laboratory findings into **Major** and **Minor** criteria. ### Why Arthralgia is the Correct Answer **Arthralgia** (joint pain without objective findings like swelling or heat) is classified as a **Minor Criterion**. In contrast, the major joint manifestation of ARF is **Polyarthritis**, which involves objective evidence of inflammation (swelling, redness, warmth) in multiple joints. Therefore, while arthralgia is a common symptom of ARF, it is not a "Major" component. ### Explanation of Incorrect Options (Major Criteria) The following are part of the **J♥NES** mnemonic for Major Criteria: * **A. Carditis (C):** Present in 50-70% of cases; it is the only component that can lead to chronic disability (Rheumatic Heart Disease). * **B. Polyarthritis (J - Joints):** Typically a migratory large-joint arthritis that responds dramatically to salicylates. * **C. Subcutaneous Nodules (N):** Small, painless, firm nodules usually found over bony prominences or tendons. ### NEET-PG High-Yield Pearls * **Revised Jones Criteria (2015):** Now differentiates between **Low-risk** and **Moderate/High-risk** populations. In high-risk populations, *monoarthritis* or *polyarthralgia* can be considered Major criteria. * **The "J♥NES" Mnemonic for Major Criteria:** * **J** - Joints (Migratory Polyarthritis) * **♥** - Carditis (Pancarditis) * **N** - Nodules (Subcutaneous) * **E** - Erythema Marginatum * **S** - Sydenham’s Chorea * **Minor Criteria:** Arthralgia, Fever, Elevated ESR/CRP, and Prolonged PR interval on ECG. * **Essential Requirement:** Evidence of a preceding Group A Streptococcal (GAS) infection (e.g., elevated ASO titer or positive throat culture) is mandatory for diagnosis, except in cases of isolated chorea or insidious carditis.

Question 38: What is the characteristic feature of early congenital syphilis?

A. Microcephaly
B. Saddle nose
C. Interstitial keratitis with sabre skin
D. Vesicular rash with bulla over palms and soles (Correct Answer)

Explanation: **Explanation:** Congenital syphilis is divided into **Early** (presenting before 2 years of age) and **Late** (presenting after 2 years). **Why Option D is correct:** The characteristic skin lesion in early congenital syphilis is **Syphilitic Pemphigus**. This presents as a vesiculobullous or maculopapular rash that specifically involves the **palms and soles**. Unlike many other neonatal rashes, these bullae are highly infectious as they contain a high load of *Treponema pallidum*. Other early features include "snuffles" (persistent rhinitis), hepatosplenomegaly, and osteochondritis (Wimberger’s sign). **Analysis of Incorrect Options:** * **Option A (Microcephaly):** This is a classic feature of the **"TORCH"** group (especially CMV and Zika virus), but it is not a hallmark of congenital syphilis. * **Option B (Saddle nose):** This is a **Late** manifestation caused by the destruction of the nasal cartilage due to persistent inflammation (gummas). * **Option C (Interstitial keratitis with sabre shin):** These are features of **Late** congenital syphilis. Interstitial keratitis is part of the **Hutchinson’s Triad** (along with sensorineural deafness and Hutchinson teeth), while Sabre shin refers to the anterior bowing of the tibia. **Clinical Pearls for NEET-PG:** * **Hutchinson’s Triad:** Interstitial keratitis, 8th Nerve deafness, and notched incisors (Late Syphilis). * **Clutton’s joints:** Symmetrical painless swelling of the knees (Late Syphilis). * **Mulberry molars:** Poorly developed cusps of the first molars (Late Syphilis). * **Drug of Choice:** Parenteral **Penicillin G** remains the gold standard for treatment.

Question 39: The term infantile polyarteritis nodosa was formerly used for which condition?

A. Goodpasture's syndrome
B. Henoch-Schönlein purpura
C. Kawasaki disease (Correct Answer)
D. Takayasu's arteritis

Explanation: **Explanation:** **Kawasaki Disease (KD)**, also known as mucocutaneous lymph node syndrome, was historically referred to as **infantile polyarteritis nodosa (IPN)**. This is because both conditions are characterized by medium-vessel vasculitis and the formation of coronary artery aneurysms. Pathologically, the vascular lesions in severe infantile cases of KD were found to be indistinguishable from the necrotizing vasculitis seen in Polyarteritis Nodosa (PAN). Today, KD is recognized as a distinct clinical entity and is the most common cause of acquired heart disease in children in developed nations. **Analysis of Incorrect Options:** * **Goodpasture’s Syndrome:** This is an anti-glomerular basement membrane (anti-GBM) disease characterized by pulmonary hemorrhage and glomerulonephritis. It is a small-vessel vasculitis, not related to the medium-vessel pathology of IPN. * **Henoch-Schönlein Purpura (IgA Vasculitis):** This is the most common small-vessel vasculitis in children, presenting with palpable purpura, arthritis, and abdominal pain. It involves IgA deposition rather than the necrotizing arteritis seen in PAN. * **Takayasu’s Arteritis:** Known as "pulseless disease," this is a large-vessel vasculitis primarily affecting the aorta and its main branches. It typically affects adolescent girls and young women, unlike the infantile presentation of KD. **Clinical Pearls for NEET-PG:** * **Diagnostic Criteria for KD:** Fever for ≥5 days plus 4 out of 5 signs (Conjunctivitis, Rash, Edema/Erythema of hands/feet, Adenopathy, Mucosal changes - "CREAM"). * **Cardiac Complication:** Coronary artery aneurysms occur in 20-25% of untreated cases. * **Treatment:** High-dose IVIG (2g/kg) and Aspirin. (Note: KD is one of the few pediatric indications for Aspirin). * **Echo Timing:** Baseline echocardiogram should be done at diagnosis and repeated at 2 and 6–8 weeks.

Question 40: Which of the following is NOT associated with Kawasaki disease?

A. Erythema
B. Posterior cervical lymphadenopathy
C. Thrombocytopenia (Correct Answer)
D. Conjunctivitis

Explanation: **Explanation:** Kawasaki Disease (KD) is an acute, systemic, medium-vessel vasculitis primarily affecting children under 5 years of age. The diagnosis is clinical, based on the presence of high-grade fever for ≥5 days plus at least four out of five major criteria. **Why Thrombocytopenia is the correct answer:** In Kawasaki disease, the characteristic hematological finding is actually **thrombocytosis** (elevated platelet count), which typically occurs during the subacute phase (2nd–3rd week). A platelet count often exceeding 4.5 lakh/mm³ is a classic marker. While rare cases of "macrophage activation syndrome" associated with KD can cause thrombocytopenia, it is not a standard feature or diagnostic criterion of the disease itself. **Analysis of Incorrect Options:** * **A. Erythema:** This refers to the polymorphous exanthema (skin rash) and erythema of the palms/soles, which are core diagnostic criteria. * **B. Posterior cervical lymphadenopathy:** Lymphadenopathy is a diagnostic criterion. It is typically **unilateral**, non-suppurative, and at least one node must be >1.5 cm. While often anterior, cervical involvement is the hallmark. * **D. Conjunctivitis:** Bilateral, non-exudative (bulbar) conjunctival congestion is a classic diagnostic feature. **High-Yield Clinical Pearls for NEET-PG:** * **CRASH and Burn Mnemonic:** **C**onjunctivitis, **R**ash, **A**denopathy, **S**trawberry tongue (and oral changes), **H**ands/feet (erythema/edema), and **Burn** (5 days of fever). * **Most Serious Complication:** Coronary artery aneurysms (occurs in 20-25% of untreated cases). * **Treatment:** IVIG (2g/kg) and High-dose Aspirin. (Note: This is one of the few pediatric conditions where Aspirin is indicated despite the risk of Reye’s syndrome). * **Echocardiography:** Should be performed at diagnosis, at 2 weeks, and 6–8 weeks.

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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