Pediatric Infections (Viral, Bacterial, Parasitic, Measles, Polio) MCQs

Pediatrics · 56 free questions with answers & explanations.

  1. A 3-year-old child presents with high fever, koplik spots on the buccal mucosa, and a maculopapular rash that started on the face and progressed downward. On which day of illness did the rash most likely appear?
  2. A 5-year-old boy develops sudden-onset high fever, severe throat pain, and difficulty swallowing. Examination shows a grayish-white membrane firmly adherent to the tonsils that bleeds on attempted removal, with tender cervical lymphadenopathy ('bull neck'). What is the MOST dangerous immediate complication?
  3. A 2-year-old child from a slum setting develops acute onset fever, headache, neck stiffness, and photophobia. CSF examination shows: turbid fluid, 1200 cells/mm3 (90% neutrophils), glucose 20 mg/dL (serum glucose 90 mg/dL), protein 250 mg/dL. CSF Gram stain shows Gram-negative diplococci. What is the DRUG OF CHOICE?
  4. A 4-year-old child presents with fever, parotid gland swelling, and severe abdominal pain. Serum amylase is markedly elevated. Which of the following is the MOST likely etiology?
  5. A 3-year-old child presents with sudden onset of flaccid paralysis of the right lower limb following a febrile illness 2 days ago. Deep tendon reflexes are absent in the affected limb. Sensation is intact. What is the MOST likely diagnosis?
  6. A 5-year-old child presents with fever, cervical lymphadenopathy, and membranous pharyngeal exudate. Culture on Loeffler serum medium grows Corynebacterium diphtheriae. The exotoxin's mechanism of action involves:
  7. A 7-year-old child develops acute flaccid paralysis (AFP) of the right leg over 48 hours, with fever that resolved before paralysis onset. CSF shows normal protein, normal glucose, and mild lymphocytic pleocytosis. The child received 3 doses of OPV in infancy but not the fourth dose. Which of the following BEST distinguishes wild poliovirus AFP from vaccine-derived poliovirus (VDPV) AFP?
  8. A 3-year-old child from Bihar presents with rash on day 4 of fever. Examination shows Koplik's spots and a maculopapular rash starting from the face and spreading downward, sparing the palms and soles. On day 7, the child develops altered consciousness and focal seizures. CSF shows lymphocytic pleocytosis with elevated protein. The MOST likely CNS complication is:
  9. A 2-year-old child is brought with high fever (39.5°C), drooling, severe odynophagia, respiratory distress, and 'tripod position.' Stridor is present. Lateral neck X-ray shows thumb-sign epiglottis. Which bacteria is the MOST LIKELY causative organism and the KEY virulence mechanism?
  10. A 6-year-old child presents with fever, severe headache, and nuchal rigidity. CSF analysis shows: protein 120 mg/dL, glucose 35 mg/dL (serum glucose 90 mg/dL), WBC 800 cells/mm³ with 90% neutrophils. CSF Gram stain shows Gram-negative diplococci. Which of the following CSF findings would most strongly support a bacterial etiology over viral meningitis?
  11. A 2-year-old unimmunized child presents with 3-day fever, cough, coryza, and conjunctivitis. On examination, there are 1–3 mm bluish-white spots on the buccal mucosa opposite the lower molars. Which of the following statements about Koplik's spots is most accurate?
  12. A 5-year-old child from a rural area is brought with progressive, asymmetric flaccid paralysis affecting the right leg, which began 5 days after a febrile illness. The child received 2 doses of OPV. CSF shows mild lymphocytic pleocytosis. Which of the following types of vaccine-associated paralytic poliomyelitis (VAPP) is most likely if this child's paralysis is caused by the polio vaccine?
  13. A 4-year-old child presents with cervical lymphadenopathy, grayish-white membrane in the oropharynx extending to the uvula, and hoarseness. The child is not vaccinated. A bull-neck appearance is noted. Which of the following complications occurs by direct spread (not via toxin) in diphtheria?
  14. A 3-year-old child presents with fever, rash, and Koplik spots on the buccal mucosa. The child developed measles despite receiving one dose of measles vaccine at 9 months. The most likely explanation is:
  15. A 2-year-old child in a tribal area develops flaccid monoplegia of the left leg following a febrile illness 3 weeks ago. No muscle wasting is noted yet. CSF shows 60 cells (predominantly lymphocytes), normal glucose, mildly elevated protein. The most appropriate confirmatory diagnostic step is:
  16. A 6-year-old child develops fever, sore throat, and a grayish-white membrane over the tonsils that bleeds on attempted removal. Neck swelling is prominent ('bull neck'). Blood pressure falls over the next few hours. The mechanism responsible for the cardiovascular complications in this disease is:
  17. A 5-year-old child presents with fever, maculopapular rash that started on the face and descended to the trunk and extremities over 3 days, Koplik spots on buccal mucosa, and bilateral conjunctivitis. On day 5 of illness, he develops worsening cough, high fever, and new lung infiltrates. What is the MOST likely pulmonary complication?
  18. A 3-year-old unvaccinated child develops an ascending flaccid paralysis starting in the lower limbs over 2 days. CSF shows normal glucose, normal protein, and normal cells. Stool and throat swab are positive for poliovirus type 1. What feature DISTINGUISHES this from Guillain-Barré syndrome (GBS)?
  19. A 10-year-old child presents with sudden-onset severe headache, neck stiffness, photophobia, and a petechial/purpuric rash that is non-blanching. Temperature is 39.5°C. What is the IMMEDIATE management priority before lumbar puncture?
  20. A 7-year-old child from a rural area is diagnosed with kala-azar (visceral leishmaniasis). After completing a full course of sodium stibogluconate (SSG), fever resolves but returns after 3 months with splenomegaly and pancytopenia. Tests confirm relapse with SSG-resistant L. donovani. What is the DRUG OF CHOICE for this child?
  21. A 5-year-old child develops high fever, extensive purpuric rash, and rapid deterioration over 12 hours. He has neck stiffness and petechiae spreading to the trunk. CSF shows neutrophilic pleocytosis, raised protein, and low glucose. Gram stain shows Gram-negative diplococci. Which antibiotic should be the FIRST choice when this diagnosis is suspected, even before CSF results, in a community setting?
  22. A 3-year-old unvaccinated child develops croup (laryngotracheobronchitis). This child had barking cough, stridor, and fever for 2 days and is now stridorous at rest with mild retractions. Westley Croup Score is 5 (moderate croup). Which treatment combination is evidence-based for this severity?
  23. A 4-year-old child with suspected enteric fever presents on day 8 of illness with fever >39°C, bradycardia, rose spots, and splenomegaly. Widal test shows O titer 1:160 and H titer 1:80 on a single sample. Blood culture is pending. Which statement about Widal test interpretation is CORRECT?
  24. A 5-year-old unvaccinated child presents with fever for 3 days, coryza, conjunctivitis, and a rash that started behind the ears and spread downward. The physician notes bluish-white spots on an erythematous base on the buccal mucosa opposite the lower molars. Which pathological mechanism causes the characteristic mucosal lesion?
  25. A 3-year-old presents with 5 days of fever, a strawberry tongue, diffuse erythematous rash with sandpaper texture sparing the perioral area, and tender anterior cervical lymphadenopathy (2.5 cm). Rapid strep antigen test is positive. Treatment is commenced. At day 14, the child develops bilateral non-purulent conjunctival injection, lip erythema, and swollen red palms and soles. Which diagnosis should now be considered?
  26. A 6-month-old infant with sickle cell disease (HbSS) presents with 2 days of fever (39.5°C), irritability, and bulging anterior fontanelle. CSF shows 1200 WBCs (90% neutrophils), protein 180 mg/dL, glucose 20 mg/dL (blood glucose 90 mg/dL), and a CSF Gram stain showing Gram-negative diplococci. The MOST appropriate antibiotic choice is:
  27. A 7-year-old unvaccinated child presents with high fever, cough, coryza, and conjunctivitis for 4 days, followed by a maculopapular rash starting behind the ears and spreading downward. On oral examination, blue-white spots on buccal mucosa are seen. The family lives in a community with low measles vaccination coverage. Which statement about the infectivity period is MOST accurate?
  28. A 2-year-old is brought with acute watery diarrhea. The stool is 'rice-water' in character, odorless, and the child has severe dehydration. Stool microscopy shows comma-shaped organisms, and vibrio toxin enzyme immunoassay is positive. The child is given intravenous Ringer's lactate. Once she can take orally, which antibiotic should be added to reduce illness duration?
  29. A 5-year-old girl is diagnosed with enteric fever. She has no clinical improvement after 5 days of cefixime. Blood culture isolates Salmonella typhi that is sensitive only to chloramphenicol and cotrimoxazole, and resistant to ampicillin, fluoroquinolones, and third-generation cephalosporins. What is the CORRECT classification and management?
  30. A 4-year-old child from Bihar presents with high fever, bilateral parotid swelling, and stiff neck. CSF shows lymphocytic pleocytosis with normal glucose. Which virus is most likely responsible and what is the characteristic complication in adolescent males?
  31. A 2-year-old presents with 5 days of fever followed by appearance of a maculopapular rash on the face that spreads centrifugally. Koplik's spots were noted on day 2. The immune evasion strategy that allows measles virus to cause profound immunosuppression for up to 2–3 years post-infection is:
  32. A 3-year-old child presents with 3 days of acute watery diarrhea, mucus, and blood. Stool microscopy shows trophozoites with ingested RBCs. After starting metronidazole, what is the purpose of adding a luminal amoebicide (diloxanide furoate) after completing the metronidazole course?
  33. A 7-year-old child presents with high-grade fever for 10 days, relative bradycardia, hepatomegaly, and rose spots on the trunk. Widal test: O titer 1:320, H titer 1:640. Blood culture pending. The most appropriate first-line antibiotic for this uncomplicated enteric fever in this child is:
  34. A 4-year-old child presents with a prodrome of high-grade fever for 3 days followed by appearance of a morbilliform rash starting from behind the ears and spreading downward. Koplik's spots are noted on the buccal mucosa. Which of the following complications is the LEADING CAUSE OF DEATH in measles in developing countries?
  35. A 5-year-old unimmunized child develops high fever, drooling, a 'hot potato' voice, and severe odynophagia. The child insists on sitting in a tripod position. Direct laryngoscopy is avoided. What is the MOST likely causal organism and the BEST initial management step?
  36. A 2-year-old child presents with 3 weeks of fever, weight loss, cough, and a cervical lymph node of 2 cm. Mantoux test reads 16 mm. Chest X-ray shows hilar adenopathy with right middle lobe consolidation. Which MOST accurately describes the mechanism of this pulmonary finding?
  37. A 5-year-old unimmunised child has fever for 3 days, coryza, conjunctivitis, and a blotchy maculopapular rash starting at the hairline. Koplik's spots are seen on the buccal mucosa. Which immunological defect is the most important complication following measles infection?
  38. A 2-year-old presents with 5 days of high fever, generalised lymphadenopathy, tonsillopharyngitis with membrane, and the Monospot (heterophile antibody) test is positive. Which virus is responsible, and which complication requires immediate intervention?
  39. A 4-year-old recently returned from an endemic area develops pallor, high intermittent fever with rigors every 48 hours, and splenomegaly. Peripheral smear shows ring trophozoites with Maurer's clefts and multiple ring forms per RBC. Which plasmodium species is responsible?
  40. A 2-year-old child has fever for 5 days, morbilliform rash, coryza, cough, and conjunctivitis. Just before the rash appeared, small white spots were seen on the buccal mucosa opposite the lower molars. The child was unvaccinated. The pathognomonic mucosal finding described is:
  41. A 5-year-old presents with fever and a distinct rash: small oval vesicles on different stages of evolution (macules, papules, vesicles, pustules, scabs simultaneously on the same area of skin), appearing first on the trunk. The MOST serious potential complication of the causative virus in an immunocompromised child is:
  42. A 10-year-old from Bihar presents with fever, rigor, and daily bouts of jaundice. Peripheral blood smear shows infected RBCs enlarged with Schüffner's dots, trophozoites showing amoeboid appearance, and absence of malarial pigment in early stages. Species identified is Plasmodium vivax. The specific danger of P. vivax in this child requiring preventive therapy is:
  43. A 3-year-old with measles develops high fever, altered sensorium, and seizures 4 days after the rash appears. CSF shows lymphocytic pleocytosis. The complication is:
  44. A 5-year-old boy develops fever, severe sore throat, a greyish-white membrane over his tonsils that bleeds on attempted removal, and marked cervical lymphadenopathy ('bull neck'). ECG shows first-degree AV block. The immediate management includes:
  45. A 2-year-old child in a measles-endemic area presents with fever, maculopapular rash starting at the hairline and progressing downward, coryza, and conjunctivitis. He develops respiratory distress and bilateral patchy lung infiltrates. The most feared complications of measles include all of the following EXCEPT:
  46. A 5-year-old child presents with a sore throat and a grayish-white pseudomembrane over the tonsils extending to the uvula. On attempted removal, the membrane bleeds. He has a 'bull neck' appearance. Myocarditis develops on day 8. The toxin responsible for cardiac and neural complications acts by:
  47. A 12-year-old child from a tribal region presents with perianal pruritus worst at night, and the mother reports seeing small white thread-like worms near the anus. The most reliable diagnostic test is:
  48. A 3-year-old boy develops high fever (40°C), cough, coryza, and conjunctivitis for 3 days. His vaccination history is incomplete. Small bluish-white spots on a red background are noted on the buccal mucosa. The following day, a maculopapular rash appears behind the ears and spreads centrifugally to the face, trunk, and limbs. He develops increasing respiratory distress. Chest X-ray shows bilateral infiltrates. What is the most likely serious complication?
  49. A 4-year-old child from a poorly immunized community develops fever, pharyngitis, and a grayish-white pseudomembrane over the tonsillar pillars extending to the uvula, which bleeds when attempts are made to remove it. The child has a 'bull neck' appearance. Which toxin mechanism is responsible for myocarditis in this condition?
  50. A 5-year-old from a rural area presents with acute onset of asymmetric flaccid paralysis of one lower limb, fever having resolved 2 days prior, and CSF showing lymphocytic pleocytosis with elevated protein and normal glucose. Which finding on EMG/nerve conduction studies would best confirm lower motor neuron involvement?
  51. A 2-year-old unvaccinated child presents with 4 days of high fever, cough, coryza, conjunctivitis, and then a maculopapular rash starting behind the ears and spreading cephalocaudally. Koplik's spots are visible on the buccal mucosa. Which of the following complications is the MOST COMMON cause of death from measles in developing countries?
  52. A 6-year-old child develops acute flaccid paralysis (AFP) of the left leg 5 days after fever. The paralysis is asymmetric, involves one limb, sensation is intact, and reflexes are absent in the affected limb. CSF shows mild pleocytosis with normal glucose and protein. What is the MOST specific confirmatory test?
  53. A 3-year-old presents with thick gray membrane over the tonsil extending to the soft palate, bull neck (cervical lymphadenopathy and soft tissue edema), and a low-grade fever. Gram stain of the membrane shows club-shaped bacilli in 'Chinese letter' arrangement. The MOST life-threatening immediate complication of this infection is:
  54. A 3-year-old child has fever for 4 days with a maculopapular rash starting on the face and spreading downward. Koplik spots were noted at the beginning. He received only 1 dose of measles vaccine at 9 months. Regarding measles complications in this child, which is the MOST feared long-term neurological complication?
  55. A child with suspected enteric fever on day 8 of illness has blood cultures negative (treated earlier at peripheral facility). The most sensitive investigation at this stage of illness for confirming typhoid is:
  56. A 2-year-old child presents with high fever, toxic appearance, drooling, muffled voice, and holds head extended (sniffing position). There is no barking cough. The most likely diagnosis and the safest immediate step is:
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