Which of the following is the pathognomonic enanthem seen in measles that appears 2–3 days before the characteristic maculopapular rash?

Explanation

## Koplik Spots: The Pathognomonic Enanthem of Measles **Key Point:** Koplik spots are small white spots with red halos appearing on the buccal mucosa (opposite molars) and are considered pathognomonic for measles. They appear 2–3 days before the characteristic exanthem and fade as the rash emerges. **High-Yield:** Koplik spots are the earliest clinical sign of measles and have high diagnostic specificity. They look like "grains of salt on a red background" and are a critical diagnostic clue when the rash has not yet appeared. **Clinical Pearl:** Koplik spots may be mistaken for aphthous ulcers or thrush in the early stage, but their timing (pre-rash), location (buccal mucosa), and appearance (white spots with red halo, NOT ulcers) distinguish them. ## Timeline of Measles Exanthem and Enanthem | Feature | Timing | Appearance | Location | |---------|--------|------------|----------| | **Koplik spots** | Days 2–3 of illness | White spots with red halo | Buccal mucosa (opposite molars) | | **Maculopapular rash** | Day 3–4 onwards | Discrete macules/papules, becomes confluent | Hairline → face → trunk → extremities | | **Rash fades** | Days 6–7 | Desquamation may occur | Follows same sequence | **Mnemonic:** **3-C-3 Rule of Measles** - **3** days of prodrome (fever, cough, coryza, conjunctivitis) - **C**oplik spots appear (enanthem) - **3** days later: rash appears (exanthem) [cite:Park 26e Ch 7]