Koplik spots are pathognomonic for which disease?

• A. Rubella
• B. Varicella
• C. Measles
• D. Hand-Foot-Mouth disease

Answer: (C)

Koplik spots are an early, highly specific sign of measles. They appear as small bluish-white lesions on a reddened buccal mucosa, usually opposite the molars, and show up during the prodromal period before the characteristic rash. This makes them a strong diagnostic clue for measles, since rubella, varicella, and hand-foot-mouth disease do not produce Koplik spots. Rubella tends to have milder fever with a pink maculopapular rash, varicella shows vesicles in crops across the body, and hand-foot-mouth presents oral ulcers with vesicles on the hands and feet. So the presence of Koplik spots points to measles.