Misdiagnosis of erythema migrans.

Background: Erythema migrans is a clinical diagnosis that carries possible long-term repercussions. Despite widespread awareness of the clinical presentation of erythema migrans, incorrect diagnosis occurs.

Methods: We describe 13 cases in which erythema migrans was misdiagnosed and discuss some pitfalls in diagnosis. These cases were seen at a tertiary referral center in Connecticut, a state where Lyme disease is endemic. The patients selected for inclusion were those who most clearly illustrate potential difficulties involved in making the diagnosis of erythema migrans.

Results: The diagnosis of erythema migrans was missed in 5 patients due to atypical presentations. Eight patients with skin eruptions closely mimicking erythema migrans were incorrectly diagnosed with erythema migrans.

Conclusions: There are pitfalls associated with the diagnosis of erythema migrans that may result in overdiagnosis or underdiagnosis.