EM Rash: Lyme Disease Rash May Not Be a Bull’s-Eye
It may spread without a bull’s-eye.
And it can be mistaken for cellulitis.
An EM rash, or erythema migrans rash, is one of the most important early signs of Lyme disease. But it does not always look like the classic bull’s-eye rash.
Some Lyme rashes appear as a red circle, red ring, expanding patch, crusted plaque, or irritated area of skin. This can make diagnosis difficult—especially when a patient does not remember a tick bite.
Clinical reality: waiting for a perfect bull’s-eye appearance can delay diagnosis.
A Case of an Atypical EM Rash
In a case report, Lorquet and colleagues described a 51-year-old woman who developed malaise, headache, neck stiffness, and a rapidly expanding rash consistent with early Lyme neuroborreliosis.
The woman did not recall a tick bite. Her rash began as a small area of redness on her upper back, then spread quickly over several days.
Clinicians initially suspected cellulitis and treated her with cephalexin and valacyclovir. Her symptoms did not improve.
When a Lyme Rash Looks Like Something Else
By the time she was reevaluated, the rash covered nearly two-thirds of her back and included a crusted plaque in the center. A second circular rash appeared behind her right ear.
Clinical pattern: an EM rash may be large, itchy, circular, crusted, or non-classic.
The authors emphasized that the bull’s-eye appearance is not the only skin finding seen in early Lyme disease.
An expanding red circle or rash should raise concern for Lyme disease—even without a bull’s-eye.
Why This Rash Was Important
The patient also had neurologic symptoms, including worsening headache and pain radiating into the neck.
After Lyme testing returned positive, she was diagnosed with Lyme neuroborreliosis, also known in Europe as Bannwarth syndrome.
Bannwarth syndrome can involve painful nerve inflammation, radiculopathy, weakness, facial palsy, and abnormal spinal fluid findings.
Treatment and Recovery
The woman was treated empirically with doxycycline while testing was pending.
Several weeks later, she had fully recovered and returned to her baseline level of functioning.
Clinical takeaway: recognizing a non-classic EM rash can lead to earlier treatment and better outcomes.
What an EM Rash Can Look Like
An EM rash may appear as:
- A red circle on the skin
- A red ring or expanding patch
- A solid red rash without central clearing
- A large plaque-like rash
- A rash mistaken for cellulitis or a skin infection
Key point: the rash’s expansion over time is often more important than whether it has a bull’s-eye shape.
An EM rash may not look like a bull’s-eye. If a red circle, ring, or expanding rash appears after possible tick exposure, Lyme disease should be considered.
Final Thought
Lyme disease can hide behind ordinary-looking skin findings.
A rash that expands, changes shape, or appears with headache, fatigue, neck pain, or neurologic symptoms deserves careful evaluation.
Key question: Could a red circle or expanding rash be Lyme disease?
Related Articles
- The many presentations of the Lyme disease rash
- Erythema migrans rash doesn’t always have a bull’s-eye appearance
- Lyme disease mimics cellulitis skin infection
References
- Schotthoefer AM, et al. The Spectrum of Erythema Migrans in Early Lyme Disease. Cureus. 2022.
- Lorquet JR, et al. Non-classical erythema migrans with Lyme neuroborreliosis. Cureus. 2023.
- Shah A, et al. Neuroinvasive Lyme disease presenting with Bannwarth syndrome. Open Forum Infect Dis. 2017.
Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
