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Am Fam Physician. 2018;98(8):474

Original Article: Clinical Diagnosis of Lyme Disease Frequently Misses the “Bull's Eye” [POEMs]

Issue Date: April 1, 2018

To the Editor: The title of this POEM1 may be misleading about the study and the synopsis appearing in American Family Physician. Specifically, the title suggests that diagnosing Lyme disease requires the bull's eye form of the erythema migrans rash. This suggestion is repeated in the Bottom Line section, which reads, “For children with suspected Lyme disease but without a classic bull's eye lesion (erythema migrans of at least 5 cm), check serology rather than rely on your clinical impression.”

In fact, the research study used the Centers for Disease Control and Prevention's (CDC's) definition of erythema migrans, which does not require a bull's eye lesion. Instead, the key portion of the CDC definition of erythema migrans is “a skin lesion that typically begins as a red macule or papule and expands over a period of days to weeks to form a large round lesion, often with partial central clearing. A single primary lesion must reach greater than or equal to 5 cm in size across its largest diameter.”2 Further, only 4% of the patients in the study had erythema migrans lesions that met the CDC definition.1

Central clearing is not needed to make the diagnosis of Lyme disease. It is often faint in appearance or not present, or it may not appear until the lesion grows larger or until more days have elapsed. A 1996 study found that only 37% of patients with Lyme disease had central clearing,3 and another article demonstrating variations on erythema migrans suggests that central clearing at the time of erythema migrans presentation occurs a minority of the time.4

Editor's Note: This letter was sent to the authors of Clinical Diagnosis of Lyme Disease Frequently Misses the “Bull's Eye,” who declined to reply.

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This series is coordinated by Kenny Lin, MD, MPH, deputy editor.

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