What skin lesion is characteristic of primary Lyme disease?

In primary Lyme disease, the skin lesion that is most characteristic is erythema migrans. This type of rash typically appears as a circular or oval-shaped patch that begins at the site of a tick bite. It often expands over time and may develop a central clearing, giving it a "bull's-eye" appearance. Erythema migrans usually presents within a few days to weeks after a tick bite and is a key indicator of Lyme disease, often accompanied by other early systemic symptoms such as fever, fatigue, and lymphadenopathy.

The other options do not correspond to the typical presentation of primary Lyme disease. A maculopapular rash is associated with various conditions, including viral illnesses but is not specific to Lyme. Vesicular lesions are typically indicative of infections like chickenpox or herpes simplex virus and are not related to Lyme disease. Nodular lesions may be found in other dermatological conditions but do not reflect the clinical picture of erythema migrans seen in Lyme disease. Thus, recognizing erythema migrans is crucial for diagnosing and treating primary Lyme disease effectively.