A unique presentation of Lyme disease rash

While Lyme disease is typically associated with a bull’s-eye rash, atypical presentations can occur. Recognizing these unique appearances is imperative to an early diagnosis and prompt treatment, especially when serological testing for Lyme disease is unreliable.

In their study, “Atypical Lyme Disease Rash: A Case Report,” Khanna et al. describe the case of a 69-year-old woman, who tested negative for Lyme disease (according to CDC criteria), yet presented with an atypical Lyme rash.

“Our patient only had one band positive on Western blot testing, which is not considered a positive result.”

“Most clinicians recognize [Lyme disease] by the typical associated bull’s-eye appearance of the erythema migrans (EM) rash. However, a diagnostic challenge occurs when an alternate appearance for the rash is present,” the authors state.

In a study of 69 people, who presented to a medical center in Wisconsin, an area endemic for Lyme disease, more than 50% of the EM lesions were homogeneous in color and only 6% exhibited the bull’s-eye appearance. And, in West Virginia only 49% of cases had the EM rash, according to a 2021 study.

Lyme disease rash: a unique appearance

The patient, who resides in West Virginia, exhibited a rash without the classic outer ring or inner clearing as seen with EM rashes. She sought medical attention for a purplish, itchy rash on her abdomen, which appeared 6 days after a tick bite. Lesions were also present underneath both breasts, along with several smaller papules on the upper arm.

The purple coloring of the rash is unique. According to one study, only 6% of EM rashes were purple.

View rash images from study.

In West Virginia, 2021 data revealed that only 49% of cases had the EM rash.

Prior to testing for Lyme disease, the woman was treated empirically with doxycycline for 14 days. One week later, there was significant improvement of the rash with no additional symptoms.

How familiar are doctors with atypical presentations of a Lyme disease rash? One study found:

• 25.7% of the participants incorrectly identified the uniformly red EM
• 43.6% incorrectly identified the disseminated EM
• 33.0% incorrectly identified the blue-purple EM presentation

Authors conclude:

• “Healthcare providers should maintain a high index of suspicion of [Lyme disease] in patients with tick bites, even without typical EM, to ensure early diagnosis and treatment.”
• “Education on diverse [Lyme disease] presentations is crucial for improving public health outcomes.”