Erythema chronicum migrans

Synonyms

Early localized Lyme disease, erythema migrans.

Definition

Erythema chronicum migrans is the characteristic dermatologic manifestation of Lyme disease.

Full Text

Erythema chronicum migrans (ECM) is the earliest clinical manifestation of Lyme disease. Only about 30% of patients recall a tick bite which preceeded the development of the lesion. Approximately 10% of patients with Lyme disease do not develop ECM, but rather present with systemic symptoms such as fever, chills, headache, and joint aches. The lesion begins at the site of tick bite and consists of an expanding erythematous macule with occasional central clearing over the course of several days. While the classic lesion is the "bullseye" with its erythematous border and central clearing, a recent study found that 59% of the lesions were homogenous and only 9% had central clearing. Because ticks prefer to take their blood meal in warm, moist locations, the axilla, inguinal region and behind the knees are frequently the...