Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 271: Which among the following diagnostic criteria is most characteristic of Kawasaki disease?

A. Periungual desquamation (Correct Answer)
B. Generalized lymphadenopathy
C. Splenomegaly
D. Exudative conjunctivitis

Explanation: **Explanation:** Kawasaki Disease (KD) is an acute, febrile, medium-vessel vasculitis primarily affecting children. The diagnosis is clinical, based on the presence of high-grade fever for ≥5 days plus at least 4 out of 5 principal clinical features. **1. Why Periungual Desquamation is Correct:** While not present in the acute phase, **periungual desquamation** (peeling of skin starting under the fingernails and toenails) is a classic, pathognomonic finding of the **subacute phase** (weeks 2–3). It is considered a hallmark of the disease's progression and is a key component of the "Extremity Changes" diagnostic criterion. **2. Why the Other Options are Incorrect:** * **Generalized Lymphadenopathy:** In KD, lymphadenopathy is typically **unilateral, cervical**, and >1.5 cm. Generalized lymphadenopathy suggests other diagnoses like EBV or malignancy. * **Splenomegaly:** This is not a feature of KD. Its presence should raise suspicion for Macrophage Activation Syndrome (MAS), a potential complication, or other systemic infections. * **Exudative Conjunctivitis:** KD causes **bilateral, non-exudative** (bulbar) conjunctival injection. The absence of discharge is a critical distinguishing factor from viral or bacterial conjunctivitis. **Clinical Pearls for NEET-PG:** * **CRASH and Burn Mnemonic:** **C**onjunctivitis (non-exudative), **R**ash (polymorphous), **A**denopathy (cervical), **S**trawberry tongue (mucositis), **H**ands/feet (edema/peeling), and **Burn** (5 days of fever). * **Most Serious Complication:** Coronary artery aneurysms (occurs in 20-25% of untreated cases). * **Investigation of Choice:** 2D-Echocardiography. * **Management:** High-dose IVIG (2g/kg) plus Aspirin. Note: This is one of the few pediatric indications for Aspirin despite the risk of Reye’s syndrome.

Question 272: A child presents with tuberculosis. Steroids are not indicated in which of the following conditions?

A. Tuberculoma
B. Endobronchial tuberculosis
C. Massive pleural effusion
D. Progressive primary pulmonary disease (Correct Answer)

Explanation: **Explanation:** In the management of pediatric tuberculosis, corticosteroids are used as an adjunct to Anti-Tubercular Treatment (ATT) primarily to reduce the inflammatory response and prevent complications like fibrosis or mechanical obstruction. **Why Progressive Primary Pulmonary Disease (PPPD) is the correct answer:** PPPD refers to the direct progression of a primary focus into pneumonia or cavitation. In this condition, the primary requirement is intensive bactericidal action (ATT). Steroids have **no proven benefit** in PPPD and may theoretically interfere with the local immune response required to contain the infection. **Analysis of Incorrect Options:** * **Tuberculoma:** Steroids are indicated if there is significant perilesional edema causing increased intracranial pressure or focal neurological deficits. * **Endobronchial Tuberculosis:** Steroids are used to reduce the inflammatory edema and granulation tissue in the airway, thereby preventing bronchial obstruction and subsequent collapse or bronchiectasis. * **Massive Pleural Effusion:** While not always mandatory, steroids are indicated in massive effusions to hasten the resolution of fluid, reduce systemic symptoms (fever/pain), and prevent pleural thickening/fibrosis. **High-Yield Clinical Pearls for NEET-PG:** * **Absolute Indications for Steroids in TB:** TB Meningitis (Stage II and III) and Miliary TB (if associated with respiratory distress or hypoxia). * **Other Indications:** Pericardial effusion (to prevent constrictive pericarditis), severe phlyctenular conjunctivitis, and renal TB (to prevent ureteric strictures). * **Standard Dose:** Prednisolone 1–2 mg/kg/day for 4–6 weeks, followed by a tapering dose.

Question 273: The rash in measles typically occurs first in which region?

A. Forehead
B. Post auricular (Correct Answer)
C. Chest
D. Neck

Explanation: **Explanation:** The correct answer is **Post-auricular**. Measles (Rubeola) is a highly contagious viral infection characterized by a specific sequence of clinical features. The rash in measles is a **maculopapular, erythematous, and blanching** eruption. **Why Post-auricular is correct:** The rash typically appears on the **4th day** of the illness (the eruptive phase). It characteristically starts **behind the ears (post-auricular)** and along the **hairline**. From there, it spreads in a **cephalocaudal** (head-to-toe) direction, moving downward to the face, neck, trunk, and finally the extremities (including palms and soles in severe cases). **Why other options are incorrect:** * **Forehead:** While the rash quickly involves the forehead and face, it classically originates behind the ears. * **Chest & Neck:** These areas are involved later as the rash spreads downward. The neck is usually involved on the first day of the rash, and the chest/trunk on the second day. **High-Yield Clinical Pearls for NEET-PG:** * **Koplik Spots:** These are the pathognomonic "grains of salt on a red base" found on the buccal mucosa opposite the lower second molars. They appear *before* the rash (prodromal stage). * **The 3 C’s:** The prodromal phase is marked by **C**ough, **C**oryza, and **C**onjunctivitis. * **Resolution:** The rash fades in the same order it appeared, often leaving behind **brownish discoloration** and **fine desquamation**. * **Vitamin A:** Supplementation is recommended for all children with measles to reduce morbidity and mortality. * **Most common complication:** Otitis media. * **Most common cause of death:** Pneumonia.

Question 274: What is the mortality rate in measles encephalitis?

A. 1-2%
B. 10-20% (Correct Answer)
C. 20-30%
D. 30-40%

Explanation: **Explanation:** Measles (Rubeola) is associated with several neurological complications, the most common being **Acute Disseminated Encephalomyelitis (ADEM)**, also known as post-measles encephalitis. This typically occurs 2–7 days after the appearance of the rash and is an immune-mediated demyelinating process. **Why 10-20% is correct:** The mortality rate for acute measles encephalitis is consistently cited in standard pediatric textbooks (like Nelson) as **10–15%**, which falls within the **10–20%** range. Beyond mortality, this condition is significant because approximately **25–40%** of survivors suffer from permanent neurological sequelae, such as intellectual disability, seizures, or deafness. **Analysis of Incorrect Options:** * **A (1-2%):** This is too low for encephalitis. This figure more closely resembles the overall case fatality rate of measles in developing countries due to respiratory complications (pneumonia). * **C & D (20-40%):** These figures are too high for acute encephalitis. While measles is severe, the acute neurological mortality rarely exceeds 20% with modern supportive care. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of death in Measles:** Pneumonia (responsible for ~60% of deaths). * **Subacute Sclerosing Panencephalitis (SSPE):** A late, progressive degenerative complication occurring 7–10 years after infection. It is 100% fatal. * **Vitamin A:** Supplementation is mandatory in all children with measles to reduce mortality and blindness. * **Modified Measles:** Occurs in partially immune individuals; it has a longer incubation period and milder symptoms.

Question 275: What is the most common cause of Reye's syndrome in children?

A. Polio virus
B. Measles virus
C. Influenza virus (Correct Answer)
D. HIV

Explanation: **Explanation:** **Reye’s Syndrome** is a rare but life-threatening condition characterized by acute non-inflammatory encephalopathy and fatty degeneration of the liver (microvesicular steatosis). It typically follows a viral prodrome. **Why Influenza is Correct:** The most common triggers for Reye’s syndrome are **Influenza (Type A and B)** and **Varicella (Chickenpox)**. The underlying pathophysiology involves mitochondrial dysfunction, which is severely exacerbated when a child with a viral infection is administered **Aspirin (salicylates)**. This leads to a failure of fatty acid oxidation, resulting in hyperammonemia, cerebral edema, and hepatic failure. **Analysis of Incorrect Options:** * **Polio virus:** Primarily affects the anterior horn cells of the spinal cord; it is not associated with the metabolic/mitochondrial failure seen in Reye’s. * **Measles virus:** While measles can cause Subacute Sclerosing Panencephalitis (SSPE) or acute encephalitis, it is not a classic trigger for Reye’s syndrome. * **HIV:** Causes chronic immunodeficiency and opportunistic infections but does not trigger the acute mitochondrial toxicity characteristic of Reye’s. **High-Yield Clinical Pearls for NEET-PG:** * **The "Aspirin Connection":** Always avoid Aspirin in children with viral fevers (except in Kawasaki disease). Use Acetaminophen (Paracetamol) instead. * **Biochemical Markers:** Characterized by elevated serum ammonia, increased AST/ALT, prolonged Prothrombin Time (PT), and **normal bilirubin** (a key diagnostic hint). * **Histopathology:** Liver biopsy shows **microvesicular steatosis** (fine droplets of fat) without significant inflammation. * **Clinical Sign:** Persistent, profuse vomiting followed by altered sensorium/delirium after a viral illness.

Question 276: Fever with all of the following characters are considered danger signs of acute encephalitis syndrome, EXCEPT:

A. Lethargy
B. Convulsion
C. Hepatosplenomegaly
D. Pain abdomen (Correct Answer)

Explanation: **Explanation:** Acute Encephalitis Syndrome (AES) is a clinical condition characterized by the acute onset of fever and a change in mental status (such as confusion, disorientation, coma, or inability to talk) and/or new-onset seizures. **1. Why "Pain Abdomen" is the correct answer:** While abdominal pain can occur in various systemic infections (like Enteric fever), it is **not** a defining danger sign or a diagnostic criterion for AES. AES primarily involves the Central Nervous System (CNS). Danger signs in AES are those that indicate increased intracranial pressure, cerebral dysfunction, or impending neurological collapse. **2. Analysis of Incorrect Options (Danger Signs):** * **Lethargy:** A change in the level of consciousness (ranging from lethargy to deep coma) is the hallmark of AES. It indicates significant cortical or brainstem involvement. * **Convulsion:** New-onset seizures (focal or generalized) are a major diagnostic criterion for AES, reflecting cortical irritability due to inflammation (encephalitis). * **Hepatosplenomegaly:** In the context of the Indian subcontinent, AES is often caused by Japanese Encephalitis, but also by **Chandipura virus** or metabolic encephalopathies like **Reye’s Syndrome**. In Reye’s syndrome or certain viral etiologies, hepatomegaly is a critical sign of systemic involvement and metabolic derangement. **Clinical Pearls for NEET-PG:** * **Definition:** AES is defined as Fever + Altered Sensorium (for >24 hours) +/- Seizures. * **Most Common Cause (India):** Historically Japanese Encephalitis (JE), but currently, "Non-JE" causes (like Enteroviruses and Scrub Typhus) are rising. * **Key Investigation:** CSF analysis is mandatory to differentiate encephalitis from meningitis. * **Management Priority:** Stabilization of Airway, Breathing, and Circulation (ABC) and management of raised Intracranial Pressure (ICP) using Mannitol or Hypertonic Saline.

Question 277: What is the minimum number of pustules required to diagnose a possible severe bacterial infection in children?

A. More than 5
B. More than 10 (Correct Answer)
C. More than 15
D. More than 20

Explanation: This question is based on the **Integrated Management of Neonatal and Childhood Illness (IMNCI)** guidelines, which are high-yield for NEET-PG. ### **Explanation of the Correct Answer** According to IMNCI protocols for young infants (0–2 months), skin pustules are categorized to determine the severity of infection: * **Possible Serious Bacterial Infection (PSBI):** Diagnosed if there are **more than 10 skin pustules** or if there is a single large abscess. This indicates a systemic risk, requiring urgent referral and injectable antibiotics. * **Local Bacterial Infection:** Diagnosed if there are **10 or fewer pustules**. This is managed with oral antibiotics and local skin care at home. The threshold of **10 pustules** is used as a clinical proxy to differentiate between a localized skin infection and a potentially disseminated or severe infection in a vulnerable neonate. ### **Analysis of Incorrect Options** * **Option A (More than 5):** While 5 pustules require treatment, they fall under the category of "Local Bacterial Infection" (≤10 pustules). * **Options C & D (More than 15/20):** These numbers exceed the diagnostic threshold. While a child with 20 pustules certainly has a severe infection, the *minimum* number required to trigger the "Severe" classification is 10. ### **High-Yield Clinical Pearls for NEET-PG** * **Other signs of PSBI:** In addition to >10 pustules, PSBI is diagnosed if the infant has: convulsions, fast breathing (≥60 bpm), severe chest indrawing, nasal flaring, grunting, bulging fontanelle, or temperature instability (>37.5°C or <35.5°C). * **Umbilical Sepsis:** If redness of the umbilicus extends to the periumbilical skin (cellulitis), it is also classified as a **Serious Bacterial Infection**. * **Treatment:** For PSBI, the standard initial treatment is Inj. Ampicillin and Inj. Gentamicin.

Question 278: What is the standard treatment for the acute phase of Kawasaki disease?

A. Aspirin
B. Intravenous steroids
C. Intravenous immunoglobulins (Correct Answer)
D. Cyclophosphamide

Explanation: **Explanation:** Kawasaki Disease (KD) is an acute, febrile, medium-vessel vasculitis that primarily affects children. The primary goal of treatment in the acute phase is to reduce systemic inflammation and, most importantly, prevent the development of **coronary artery aneurysms (CAAs)**. **Why Option C is Correct:** **Intravenous Immunoglobulin (IVIG)** is the gold standard treatment. When administered within the first 10 days of fever onset (ideally by day 7), it reduces the risk of CAAs from approximately 25% to less than 5%. It exerts a generalized anti-inflammatory effect by modulating cytokine production and neutralizing bacterial superantigens. **Analysis of Incorrect Options:** * **Option A (Aspirin):** While high-dose Aspirin is used alongside IVIG in the acute phase for its anti-inflammatory and anti-pyretic effects, it **does not** significantly reduce the incidence of coronary aneurysms when used alone. Therefore, it is considered adjunctive, not the primary standard. * **Option B (Steroids):** These are generally reserved for "IVIG-resistant" cases or high-risk patients (e.g., Kobayashi score). They are not the first-line standard for all patients. * **Option C (Cyclophosphamide):** This is a cytotoxic agent used in severe systemic vasculitides like Granulomatosis with Polyangiitis, but it has no role in the standard management of KD. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnosis:** Clinical diagnosis requires Fever for ≥5 days + 4 out of 5 criteria (Conjunctivitis, Rash, Edema/Erythema of hands/feet, Adenopathy, Mucositis/Strawberry tongue). * **Aspirin Dosing:** High dose (80–100 mg/kg/day) in the acute phase; Low dose (3–5 mg/kg/day) in the subacute phase for anti-platelet effect. * **Vaccination:** Live vaccines (MMR, Varicella) must be deferred for **11 months** after IVIG administration due to potential interference with the immune response. * **Most common cause** of acquired heart disease in children in developed nations.

Question 279: Hutchinson's triad is seen in which of the following conditions?

A. Primary syphilis
B. Congenital syphilis (Correct Answer)
C. Secondary syphilis
D. Tertiary syphilis

Explanation: **Explanation:** **Hutchinson’s triad** is a classic clinical manifestation of **Late Congenital Syphilis** (occurring in children >2 years of age). It is caused by the transplacental transmission of *Treponema pallidum* from an infected mother to the fetus, leading to chronic inflammatory changes during development. The triad consists of: 1. **Hutchinson’s Teeth:** Notched, peg-shaped permanent upper central incisors. 2. **Interstitial Keratitis:** Chronic inflammation of the corneal stroma leading to corneal scarring and potential blindness (usually appearing between ages 5–15). 3. **Sensorineural Hearing Loss:** Caused by eighth cranial nerve (vestibulocochlear) involvement. **Why other options are incorrect:** * **Primary Syphilis:** Characterized by a painless **chancre** at the site of inoculation and regional lymphadenopathy. * **Secondary Syphilis:** Presents with systemic symptoms, including a generalized maculopapular rash (involving palms and soles), **condyloma lata**, and lymphadenopathy. * **Tertiary Syphilis:** Occurs years after the initial infection, characterized by **gummas** (granulomatous lesions), cardiovascular syphilis (aortitis), and neurosyphilis (tabes dorsalis). **NEET-PG High-Yield Pearls:** * **Mulberry Molars:** Another dental finding in congenital syphilis involving the first molars (multiple cusps). * **Clutton’s Joints:** Symmetrical painless swelling of the knees (hydrarthrosis). * **Saber Shins:** Anterior bowing of the tibia due to periostitis. * **Early Congenital Syphilis (<2 years):** Look for **snuffles** (hemorrhagic rhinitis), palmoplantar rash, and pseudoparalysis of Parrot.

Question 280: After 3 days of fever, a patient developed a macular erythematous rash that lasted for 48 hours on the 4th day of fever. What is the most likely diagnosis?

A. Fifth disease
B. Rubella
C. Measles
D. Roseola infantum (Correct Answer)

Explanation: **Explanation:** The clinical hallmark of **Roseola Infantum** (also known as Exanthema Subitum or Sixth Disease) is a high-grade fever that lasts for 3 to 5 days and **subsides abruptly (defervescence)**, immediately followed by the appearance of a macular or maculopapular rash. This "fever-ends-rash-appears" sequence is a classic NEET-PG favorite. The rash typically starts on the trunk and spreads to the neck and extremities, lasting for 24 to 48 hours. It is caused by **Human Herpesvirus 6 (HHV-6)**. **Why other options are incorrect:** * **Fifth Disease (Erythema Infectiosum):** Caused by Parvovirus B19. It typically presents with a "slapped-cheek" appearance followed by a reticular (lace-like) rash on the limbs. The rash appears *after* the prodromal symptoms have resolved, but the fever is usually low-grade. * **Rubella (German Measles):** The rash and fever occur **simultaneously**. A key feature is prominent post-auricular and suboccipital lymphadenopathy. The rash disappears by the third day ("3-day measles"). * **Measles (Rubeola):** The fever **increases** when the rash appears (peak fever at rash onset). It is characterized by the 3 Cs (Cough, Coryza, Conjunctivitis) and Koplik spots. **High-Yield Clinical Pearls for NEET-PG:** * **Nagayama Spots:** Erythematous papules on the soft palate and uvula seen in Roseola. * **Febrile Seizures:** Roseola is the most common viral cause of febrile seizures in infants due to the rapid rise in temperature. * **Age Group:** Most common in children aged 6 months to 2 years.

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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