RT Book, Section A1 Hardin, J. Matthew A2 Knoop, Kevin J. A2 Stack, Lawrence B. A2 Storrow, Alan B. A2 Thurman, R. Jason SR Print(0) ID 1181043836 T1 Erythema Migrans T2 The Atlas of Emergency Medicine, 5e YR 2021 FD 2021 PB McGraw-Hill PP New York, NY SN 9781260134940 LK accessemergencymedicine.mhmedical.com/content.aspx?aid=1181043836 RD 2024/03/29 AB Borrelia burgdorferi is the tick-borne spirochete responsible for Lyme disease, and erythema migrans is the 1st cutaneous sign. Erythema migrans typically presents 1 to 2 weeks after the bite. The initial prodromal symptoms of fever, myalgias, arthralgias, and headache are followed by a macule or papule progressing to a plaque at the bite site. This plaque expands (usually to 5 cm or larger) its red, raised border as it clears centrally, leading to an annular appearance (“bull’s eye”). The plaque may burn and is rarely pruritic. Less frequently, secondary erythema migrans–like lesions can appear due to multiple bites or spirochetemia. Erythema migrans is seen in 60% to 90% of patients and represents the early localized stage.