Infectious Diseases — MCQs
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What is the recommended treatment for an infant born to a mother with active tuberculosis?
A 5-year-old child presents with a febrile illness characterized by cough and a blotchy rash. The child has not received routine pediatric care. On examination, there is lymphadenopathy and an erythematous, maculopapular rash behind the ears and along the hairline, involving the neck and, to a lesser extent, the trunk. Examination of this patient's oropharynx would likely reveal which lesion?
Which of the following vasculitides is typically not seen in adults?
Cancrum oris is associated with all the following EXCEPT:
Forcheimer sign is seen in which of the following conditions?
Which statement is true regarding the transmission of HIV to an infant from an infected mother?
A rapid antigen test for meningitis organisms can be performed on which of the following specimens EXCEPT?
Koplik spots are seen in which of the following conditions?
A child presents with a history of high fever for 4 days, followed by seizures. A rash develops on the trunk the day after the fever subsides. What is the most probable diagnosis?
A 12.6-month-old baby was brought with difficulty in feeding. The child was found to be hypotonic with a weak gag. The child is on breast milk, and the mother also gives honey to the child during periods of excessive crying. What is the causative agent?
Infectious Diseases Indian Medical PG Practice Questions and MCQs
Question 301: What is the recommended treatment for an infant born to a mother with active tuberculosis?
- A. Isoniazid prophylaxis (Correct Answer)
- B. No treatment required
- C. Full treatment with Isoniazid, Rifampicin, and Ethambutol
- D. Treatment with Isoniazid and Rifampicin
Explanation: **Explanation:** The management of a neonate born to a mother with active tuberculosis (TB) focuses on preventing the high risk of primary infection and progression to disseminated disease (like TB meningitis) in the infant. **Why Option A is Correct:** According to the **National Tuberculosis Elimination Program (NTEP)** and WHO guidelines, if a mother has active pulmonary TB, the neonate should be started on **Isoniazid (INH) prophylaxis** at a dose of **5 mg/kg/day for 6 months**. This is because the infant is considered a "high-risk contact." BCG vaccination should be deferred until the completion of the 6-month INH course. After 6 months, if the infant is asymptomatic and the Mantoux test/Chest X-ray is negative, INH is stopped and BCG is administered. **Why Other Options are Incorrect:** * **Option B:** Incorrect because neonates have immature cell-mediated immunity; exposure without prophylaxis leads to a very high rate of progression to active disease. * **Options C & D:** These represent "Treatment" rather than "Prophylaxis." Full multi-drug therapy is only indicated if the neonate shows clinical signs of **Congenital TB** or has a positive evaluation (e.g., abnormal Chest X-ray or positive gastric aspirate for AFB). **High-Yield Clinical Pearls for NEET-PG:** * **Breastfeeding:** It is **not contraindicated**. The mother should continue breastfeeding while wearing a mask and practicing cough hygiene. * **Congenital TB:** The most common site of the primary complex in congenital TB is the **Liver** (due to umbilical vein spread), whereas in post-natal TB, it is the **Lungs**. * **Separation:** The infant should **not** be separated from the mother unless she is too ill to care for the child or has MDR-TB. * **Pyridoxine:** Should be supplemented (1 mg/kg) along with INH to prevent peripheral neuropathy.
Question 302: A 5-year-old child presents with a febrile illness characterized by cough and a blotchy rash. The child has not received routine pediatric care. On examination, there is lymphadenopathy and an erythematous, maculopapular rash behind the ears and along the hairline, involving the neck and, to a lesser extent, the trunk. Examination of this patient's oropharynx would likely reveal which lesion?
- A. Adherent thin, whitish patch on gingiva
- B. Cold sores on the lips
- C. Curdy white material overlying an erythematous base on the oral mucosa
- D. Multiple small white spots on the buccal mucosa (Correct Answer)
Explanation: This clinical scenario describes a classic presentation of **Measles (Rubeola)**. The diagnosis is suggested by the triad of cough, coryza, and conjunctivitis (the "3 Cs"), high fever, and a characteristic maculopapular rash that begins behind the ears and at the hairline before spreading cephalocaudally. The lack of routine pediatric care implies the child is unvaccinated. ### Why the Correct Answer is Right The pathognomonic oral finding in Measles is **Koplik spots**. These are described as multiple small, bluish-white spots on an erythematous base, typically located on the buccal mucosa opposite the lower second molars. They appear 1–2 days before the rash and are the hallmark of the prodromal phase. ### Why the Other Options are Wrong * **Option A:** Adherent thin, whitish patches on the gingiva are not characteristic of any specific pediatric exanthem; however, a thick, greyish adherent membrane in the pharynx would suggest **Diphtheria**. * **Option B:** Cold sores (herpes labialis) are caused by **Herpes Simplex Virus-1 (HSV-1)** and present as vesicular lesions on the lips, not associated with the specific rash pattern of measles. * **Option C:** Curdy white material that can be scraped off to reveal an erythematous base is characteristic of **Oral Candidiasis (Thrush)**, often seen in immunocompromised states or after antibiotic use. ### High-Yield Clinical Pearls for NEET-PG * **Etiology:** RNA Paramyxovirus (Genus *Morbillivirus*). * **Rash Progression:** Starts behind the ears $\rightarrow$ Face $\rightarrow$ Trunk $\rightarrow$ Extremities (Cephalocaudal spread). It disappears in the same order, leaving behind **brownish discoloration** and fine desquamation. * **Vitamin A:** Supplementation is mandatory in all children with measles to reduce morbidity and mortality (especially from pneumonia and blindness). * **Complications:** Most common is **Otitis Media**; most common cause of death is **Pneumonia**; most serious late complication is **SSPE** (Subacute Sclerosing Panencephalitis).
Question 303: Which of the following vasculitides is typically not seen in adults?
- A. Takayasu arteritis
- B. Susac syndrome
- C. Henoch-Schönlein purpura
- D. Kawasaki disease (Correct Answer)
Explanation: **Explanation:** **Kawasaki Disease (KD)** is the correct answer because it is an acute, self-limiting systemic vasculitis that almost exclusively affects infants and young children (85% of cases occur under age 5). While rare adult-onset cases exist, it is classically defined as a pediatric condition. It is a medium-vessel vasculitis with a predilection for the coronary arteries. **Analysis of Options:** * **Takayasu Arteritis (A):** Known as "pulseless disease," this large-vessel vasculitis typically affects young women (usually between ages 15 and 40). It is a classic adult/adolescent diagnosis. * **Susac Syndrome (B):** A rare microangiopathy characterized by the clinical triad of encephalopathy, branch retinal artery occlusions, and sensorineural hearing loss. It primarily affects young adults (ages 20–40). * **Henoch-Schönlein Purpura (C):** While HSP is the most common vasculitis in children, it is frequently seen in adults as well. In adults, the disease often presents with a more severe clinical course and a higher risk of significant renal involvement compared to children. **High-Yield Clinical Pearls for NEET-PG:** * **Kawasaki Diagnostic Criteria (CRASH and Burn):** **C**onjunctivitis (bilateral, non-exudative), **R**ash (polymorphous), **A**denopathy (cervical, usually unilateral), **S**trawberry tongue (and oral mucosal changes), **H**ands/feet (edema/desquamation), and **Burn** (High-grade fever for ≥5 days). * **Complication:** Coronary artery aneurysms are the most feared complication; **Echocardiography** is the mandatory initial investigation. * **Treatment:** High-dose IVIG + Aspirin (Note: This is one of the few pediatric indications where Aspirin is used despite the risk of Reye’s syndrome).
Question 304: Cancrum oris is associated with all the following EXCEPT:
- A. Malnutrition
- B. Inflammatory swelling
- C. Vitamin deficiency
- D. None of the above (Correct Answer)
Explanation: **Explanation:** **Cancrum Oris**, also known as **Noma**, is a devastating gangrenous stomatitis that leads to the rapid destruction of orofacial tissues. It primarily affects children (ages 2–6) in developing countries who are severely immunocompromised. **Why "None of the above" is correct:** The question asks which of the listed factors is *not* associated with Cancrum Oris. However, all three options (A, B, and C) are classic hallmarks or predisposing factors of the disease. Since all are associated, "None of the above" is the correct choice. * **Option A (Malnutrition):** This is the most significant predisposing factor. Severe Protein-Energy Malnutrition (PEM) weakens the immune system, allowing opportunistic oral flora to become invasive. * **Option B (Inflammatory swelling):** The clinical progression of Noma begins with a small intra-oral ulcer, followed by rapid, painful, **edematous inflammatory swelling** of the cheek or lip, which quickly progresses to necrosis. * **Option C (Vitamin deficiency):** Deficiencies in Vitamin B-complex and Vitamin C are frequently documented in these patients, further compromising mucosal integrity and immune response. **High-Yield Clinical Pearls for NEET-PG:** * **Microbiology:** It is a polymicrobial infection, but the key organisms involved are ***Fusobacterium necrophorum*** and ***Prevotella intermedia***. * **Preceding Infections:** It often follows a debilitating viral illness, most commonly **Measles**, but also Herpes simplex or Scarlet fever. * **Pathogenesis:** It is characterized by **rapidly spreading gangrene** that does not respect anatomical boundaries (bone and soft tissue are both destroyed). * **Treatment:** Management involves high-dose antibiotics (Penicillin/Metronidazole), nutritional rehabilitation, and delayed reconstructive surgery.
Question 305: Forcheimer sign is seen in which of the following conditions?
- A. Infectious mononucleosis
- B. Scarlet fever
- C. Rubella (Correct Answer)
- D. Rubeola
Explanation: **Explanation:** **Forchheimer sign** is a clinical finding characterized by small, reddish spots (petechiae) on the soft palate. It is seen in approximately 20% of patients with **Rubella** (German Measles). While it occurs during the prodromal phase or on the first day of the rash, it is not pathognomonic as it can occasionally be seen in other conditions. **Analysis of Options:** * **Rubella (Correct):** Forchheimer spots are a classic association. Rubella is also characterized by post-auricular and suboccipital lymphadenopathy and a rash that spreads cephalocaudally. * **Infectious Mononucleosis:** While palatal petechiae can occur in EBV infection, they are not referred to as Forchheimer spots. IM is better known for the triad of fever, pharyngitis, and lymphadenopathy. * **Scarlet Fever:** This is associated with **Pastia’s lines** (petechiae in skin folds) and a **Strawberry tongue** (white then red), caused by Group A Streptococcus. * **Rubeola (Measles):** The hallmark enanthem here is **Koplik spots** (bluish-white spots on an erythematous base opposite the lower molars), which are pathognomonic. **High-Yield Clinical Pearls for NEET-PG:** 1. **Koplik spots:** Measles (Rubeola). 2. **Forchheimer spots:** Rubella. 3. **Nagayama spots:** Roseola Infantum (HHV-6). 4. **Pastia’s lines/Strawberry tongue:** Scarlet Fever. 5. **Congenital Rubella Syndrome (CRS) Triad:** Cataract, Sensorineural hearing loss, and PDA (Patent Ductus Arteriosus).
Question 306: Which statement is true regarding the transmission of HIV to an infant from an infected mother?
- A. Administer zidovudine during labor. (Correct Answer)
- B. There is a 25% chance of vertical transmission.
- C. Avoid breastfeeding.
- D. Vaccinate the infant with OPV and MMR.
Explanation: **Explanation:** The prevention of mother-to-child transmission (PMTCT) of HIV is a high-yield topic for NEET-PG. The goal is to reduce the viral load in the mother and provide pre/post-exposure prophylaxis to the infant. **1. Why Option A is Correct:** Intrapartum transmission accounts for the majority of vertical transmission cases. Administering **Zidovudine (AZT)** intravenously during labor (or orally in resource-limited settings) significantly reduces the risk by providing systemic prophylaxis to the fetus during the period of highest exposure to maternal blood and vaginal secretions. **2. Analysis of Incorrect Options:** * **Option B:** Without intervention, the risk of transmission is approximately **25–40%**. However, with modern ART and PMTCT protocols, this risk can be reduced to **less than 1–2%**. * **Option C:** In developing countries like India (NACO guidelines), **exclusive breastfeeding** for the first 6 months is recommended if replacement feeding is not "Acceptable, Feasible, Affordable, Sustainable, and Safe" (AFASS). Mixed feeding should be strictly avoided as it increases the risk of transmission via gut inflammation. * **Option D:** While most routine vaccines are safe, **MMR** is a live vaccine and is generally contraindicated in HIV-infected children with severe immunosuppression (CD4 <15%). **OPV** is being replaced by IPV in many protocols to prevent vaccine-associated paralytic poliomyelitis (VAPP) in immunocompromised hosts. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Efavirenz-based regimens are now replaced by **Dolutegravir (DTG)** based regimens in pregnant women. * **Infant Prophylaxis:** Nevirapine (NVP) or Zidovudine is given to the infant for 6–12 weeks. * **Diagnosis in Infants:** Gold standard is **HIV DNA PCR** (at 6 weeks); Antibody tests (ELISA) are unreliable until 18 months due to persisting maternal antibodies. * **Mode of Delivery:** Elective C-section reduces risk but is not mandatory if the maternal viral load is <1000 copies/mL.
Question 307: A rapid antigen test for meningitis organisms can be performed on which of the following specimens EXCEPT?
- A. Blood
- B. Cerebrospinal fluid (CSF)
- C. Urine
- D. Throat swab (Correct Answer)
Explanation: **Explanation:** Rapid Antigen Detection Tests (RADT), such as Latex Agglutination tests, are designed to detect soluble capsular polysaccharide antigens of common meningeal pathogens (e.g., *S. pneumoniae*, *N. meningitidis*, *H. influenzae* type b, and *G.BS*). These antigens are released into sterile body fluids during an active, systemic, or localized infection. **Why Throat Swab is the Correct Answer:** A throat swab is used to identify **colonization** or local respiratory infection. Many healthy individuals are asymptomatic carriers of *N. meningitidis* or *S. pneumoniae* in their nasopharynx. Detecting antigens in a throat swab does not differentiate between harmless colonization and invasive meningitis. Therefore, it is not a diagnostic specimen for meningitis. **Analysis of Other Options:** * **CSF:** This is the primary specimen. Antigen detection in CSF is highly specific and remains useful even if the patient has already received antibiotics (which may cause a negative culture). * **Urine:** Capsular antigens (especially from *H. influenzae* and *S. pneumoniae*) are excreted by the kidneys and concentrated in the urine, making it a non-invasive and effective sample for rapid testing. * **Blood:** During septicemia associated with meningitis, bacterial antigens are present in the serum and can be detected via RADT. **Clinical Pearls for NEET-PG:** * **Latex Agglutination:** The most common method used for rapid antigen detection in meningitis. * **Advantage:** It can detect antigens even when bacteria are non-viable (e.g., post-antibiotic therapy). * **Limitation:** A negative RADT does not rule out meningitis; **CSF Culture** remains the "Gold Standard" for diagnosis. * **Specific Pathogen:** For *Cryptococcus neoformans*, the CrAg (Cryptococcal Antigen) test in CSF is more sensitive than India Ink preparation.
Question 308: Koplik spots are seen in which of the following conditions?
- A. Mumps
- B. Influenza
- C. Rubella
- D. Measles (Correct Answer)
Explanation: **Explanation:** **Koplik spots** are the pathognomonic clinical sign of **Measles (Rubeola)**. They are small, irregular, bluish-white grains on an erythematous base (often described as "grains of salt on a red background") found on the buccal mucosa, typically opposite the lower second molars. They appear during the **prodromal stage**, approximately 48 hours before the characteristic maculopapular rash, and disappear as the rash breaks out. **Analysis of Options:** * **Mumps:** Characterized by painful swelling of the parotid glands (parotitis). It does not feature an enanthem like Koplik spots. * **Influenza:** A respiratory viral infection presenting with high fever, cough, and myalgia; it lacks specific oral mucosal findings. * **Rubella (German Measles):** While it presents with a rash, its characteristic oral finding is **Forchheimer spots** (small, red petechiae on the soft palate), which are not pathognomonic. **NEET-PG High-Yield Pearls:** * **Pathognomonic Sign:** Koplik spots = Measles. * **Timeline:** They appear in the prodromal phase and fade as the rash starts (which spreads in a cephalocaudal direction). * **Vitamin A:** Supplementation is crucial in measles management to reduce morbidity and mortality (especially ocular complications). * **Complications:** The most common complication is Otitis Media; the most common cause of death is Pneumonia; the most dreaded late complication is SSPE (Subacute Sclerosing Panencephalitis).
Question 309: A child presents with a history of high fever for 4 days, followed by seizures. A rash develops on the trunk the day after the fever subsides. What is the most probable diagnosis?
- A. Roseola infantum (Correct Answer)
- B. Measles
- C. Rubella
- D. Varicella
Explanation: ### Explanation **Correct Answer: A. Roseola Infantum (Exanthema Subitum)** The clinical presentation described is classic for **Roseola infantum**, caused by **Human Herpesvirus 6 (HHV-6)**. The hallmark of this disease is a high-grade fever (often >103°F) lasting 3–5 days in a child who otherwise appears relatively well. The most defining feature is that the **rash appears only after the fever subsides** (defervescence). Because the fever rises so rapidly, **febrile seizures** are a common complication, occurring in approximately 10–15% of cases. The rash is typically maculopapular, starting on the trunk and spreading to the neck and extremities. **Why other options are incorrect:** * **Measles (Rubeola):** The rash appears at the *peak* of the high fever, not after it subsides. It is preceded by the "3 Cs" (Cough, Coryza, Conjunctivitis) and Koplik spots. * **Rubella (German Measles):** Presents with a low-grade fever and prominent post-auricular or suboccipital lymphadenopathy. The rash and fever occur simultaneously. * **Varicella (Chickenpox):** Characterized by a pruritic, pleomorphic rash (vesicles, papules, and crusts in different stages) that appears while the patient is still febrile. **NEET-PG High-Yield Pearls:** * **Etiology:** HHV-6 (most common) and HHV-7. * **Nagayama Spots:** Erythematous papules on the soft palate and uvula (seen in some Roseola patients). * **Age Group:** Most common in infants aged 6 months to 2 years. * **Sequence:** High Fever → Fever drops (Defervescence) → Rash appears. This sequence is unique to Roseola.
Question 310: A 12.6-month-old baby was brought with difficulty in feeding. The child was found to be hypotonic with a weak gag. The child is on breast milk, and the mother also gives honey to the child during periods of excessive crying. What is the causative agent?
- A. Gram positive aerobic coccus
- B. Gram positive anaerobic bacillus
- C. Toxin produced by gram positive anaerobic bacillus (Correct Answer)
- D. Echovirus
Explanation: ### Explanation The clinical presentation of a young infant with **hypotonia** (floppy baby), **weak gag reflex**, and **difficulty feeding** following the ingestion of **honey** is a classic description of **Infantile Botulism**. **1. Why the Correct Answer is Right:** Infantile botulism is caused by *Clostridium botulinum*, which is a **Gram-positive, anaerobic, spore-forming bacillus**. Unlike adult botulism (which usually results from ingesting preformed toxins in canned food), infants ingest **spores** (commonly found in honey or soil). These spores germinate in the infant's immature gut, colonize it, and release the **botulinum neurotoxin** in vivo. The toxin irreversibly binds to the presynaptic cholinergic receptors, preventing the release of acetylcholine at the neuromuscular junction, leading to descending flaccid paralysis. **2. Why the Other Options are Wrong:** * **Option A (Gram-positive aerobic coccus):** This describes organisms like *Staphylococcus* or *Streptococcus*. While they cause various pediatric infections, they do not present with acute flaccid paralysis or honey-related ingestion. * **Option B (Gram-positive anaerobic bacillus):** While *C. botulinum* is the organism, the clinical manifestations (the paralysis and symptoms) are directly caused by the **toxin** it produces, not the bacteria itself. In medical exams, the "toxin" is the more precise causative agent for the pathology. * **Option D (Echovirus):** This is a common cause of viral meningitis or hand-foot-mouth disease in children, but it does not cause the "floppy baby" syndrome associated with honey ingestion. **3. NEET-PG High-Yield Pearls:** * **Classic Triad:** Constipation (earliest sign), followed by cranial nerve palsies (weak gag, ptosis), and generalized hypotonia. * **Source:** Honey is the most commonly identified dietary reservoir; hence, honey is contraindicated in children **<1 year of age**. * **Diagnosis:** Identification of spores or toxin in the **stool** (Serum toxin levels are often negative in infants). * **Treatment:** Human-derived Botulism Immune Globulin (BIG-IV). Avoid antibiotics like aminoglycosides as they can potentiate neuromuscular blockade.
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
Practice Questions
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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