A 4-year-old child presents with a 3-day history of fever, coryza, cough, and conjunctivitis. On day 4, small white lesions with an erythematous base are noted on the buccal mucosa opposite the molars. On day 5, a maculopapular rash appears on the face and spreads downward. What is the causative agent?

• A Measles virus ✓
• B Parvovirus B19
• C Human herpesvirus 6
• D Group A Streptococcus

Explanation

Koplik spots (white lesions on buccal mucosa opposite molars) are pathognomonic of measles, appearing 1-2 days before the rash. The prodrome includes the three Cs: cough, coryza, and conjunctivitis. The rash begins on the face and spreads downward. Human herpesvirus 6 causes roseola infantum (exanthem subitum). Parvovirus B19 causes erythema infectiosum (slapped cheek). Group C Streptococcus causes scarlet fever.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.