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?

• A They appear simultaneously with the maculopapular rash
• B They persist for 7-10 days after the rash appears
• C They are pathognomonic of measles and appear 1-2 days before the rash ✓
• D They also occur in rubella and are not specific to measles

Explanation

Koplik's spots are pathognomonic of measles (rubeola). They appear on the buccal mucosa (and occasionally lower lip/gingiva) approximately 1-2 days before the maculopapular rash erupts and fade as the rash develops over 1-2 days. Their recognition in the prodromal (pre-exanthem) phase allows early diagnosis before the exanthem appears. They are not seen in rubella (which has Forchheimer spots on the soft palate, non-pathognomonic). Koplik's spots do not persist for 7-10 days after rash onset; they disappear rapidly once the rash starts.

Reference: Ghai Essential Pediatrics, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.