Which skin finding is characteristic of early localized Lyme disease?

• A. Erythema migrans
• B. Vesicular rash
• C. Petechial rash
• D. Maculopapular rash

Answer: (A)

Early localized Lyme disease is marked by an expanding erythematous skin lesion at the site of the tick bite, known as erythema migrans. This rash often begins as a small red spot and grows over days to weeks, frequently developing a central clearing that gives a bulls-eye appearance. It reflects the local spirochetal infection with Borrelia burgdorferi and is the characteristic skin finding in the initial stage, especially in people who have been in endemic areas with possible tick exposure. The other rash types—vesicular, petechial, or a non-specific maculopapular rash—do not fit the typical presentation of early localized Lyme disease and are associated with different diseases or later stages. If a patient has a classic expanding red lesion after a tick bite in an endemic area, erythema migrans is the best explanation.