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Difficulty: MediumPediatric Infectious Diseases

Match each pediatric clinical presentation with the most likely causative pathogen.

  • A seven-year-old female is evaluated for a brightly erythematous rash on both cheeks, followed two days later by a lacy, reticular rash on her extremities.Parvovirus B19
  • A four-year-old male child exhibits three days of high fever that abruptly resolves, immediately followed by a blanching maculopapular rash beginning on his trunk.Human herpesvirus 6
  • An unvaccinated six-year-old male presents with cough, coryza, and conjunctivitis, followed by a maculopapular rash spreading cephalocaudally. Small whitish lesions are seen on the buccal mucosa.Measles (Rubeola) virus
  • A five-year-old female presents with a sore throat, fever, and a diffuse, finely papular erythematous rash that spares the circumoral area. Her tongue has prominent red papillae.Streptococcus pyogenes

Answer

The presentations map to Parvovirus B19 (erythema infectiosum), Human herpesvirus 6 (roseola infantum), Measles virus (rubeola), and Streptococcus pyogenes (scarlet fever), respectively.
Each clinical vignette provides pathognomonic features for a specific pediatric infection. Parvovirus B19 causes the classic 'slapped-cheek' appearance. Human herpesvirus 6 causes roseola, uniquely characterized by defervescence followed by a rash. Measles virus presents with the '3 Cs' and Koplik spots. Streptococcus pyogenes produces an erythrogenic toxin responsible for the sandpaper-like rash and strawberry tongue of scarlet fever.

Step-by-Step Solution

1
Analyze the exanthem timing and morphology for the seven-year-old.
The slapped-cheek and reticular rash pattern strongly indicates erythema infectiosum.
Parvovirus B19 exhibits this specific biphasic clinical course and rash morphology.
2
Evaluate the fever and rash chronology for the four-year-old.
The abrupt cessation of fever coincident with the onset of a truncal rash is diagnostic for roseola infantum.
Human herpesvirus 6 is the primary etiology for this classic fever-to-rash transition.
3
Assess the prodromal symptoms and mucosal findings in the unvaccinated six-year-old.
Cough, coryza, conjunctivitis, and Koplik spots precede the rash of measles.
These findings are highly specific for infection with the Measles virus.
4
Identify the etiology of the pharyngitis and distinct rash in the five-year-old.
A sandpaper-like rash with a strawberry tongue in the setting of pharyngitis defines scarlet fever.
This is a toxin-mediated disease caused by Group A Streptococcus (Streptococcus pyogenes).

Key Concept

Clinical differentiation of classic pediatric exanthems based on prodrome, rash morphology, and illness chronology.
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Pediatric Infectious Diseases

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