Erythema chronicum migrans

Erythema chronicum migrans is the classical immune-mediated skin lesion which occurs at the site of the bite in Lyme disease some 3 to 30 days (usually around 7 days) after the bite by the Ixodes genus tick (1).

The tick bite leaves a red macule or papule which a third of patients remember which approximately one week later expands to produce a hot, painless annular/target lesion (Bull’s eye appearance) (1). The expansion gives rise to the migrans part of the name.

Erythema chronicum migrans is this annular lesion with central clearing which may be some 16cm diameter. The commonest sites for these lesions are the thigh, groin and axilla (1).

• in 2-18% of cases, erythema migrans is multiple (2)
• untreated erythema migrans may persist for several weeks and occasionally months (2)

Click here for example images of this condition

Reference:

• (1) The Centers for Disease Control and Prevention - Lyme Disease (accessed 27/5/2020).
• (2) Kullber BJ et al. Lyme borreliosis: diagnosis and management.BMJ 2020;369:m1041.