Atypical Lyme Disease Rash With Negative Testing

Rash did not look like a bull’s-eye
Lyme testing was initially negative
Diagnosis depended on clinical judgment

Case: When the Rash and Test Don’t Match

A common clinical pattern is mismatch. Lyme disease may be present even when testing is negative and the rash does not appear typical.

In their study, “Atypical Lyme Disease Rash: A Case Report,” Khanna and colleagues describe a 69-year-old woman with an unusual rash and negative Lyme testing.

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

Lyme Rashes Are Often Not Classic

Many Lyme rashes do not appear as the classic bull’s-eye.

• More than half are uniformly colored
• Only a small percentage show central clearing
• Some patients never recognize a rash at all

These variations are part of the broader spectrum described in our Lyme disease symptoms guide.

A Unique Rash Presentation

The patient developed a purplish, itchy rash on her abdomen 6 days after a tick bite.

• No outer ring or central clearing
• Additional lesions under both breasts
• Smaller papules on the upper arm

Purple coloration is uncommon but documented.

View rash images from the study.

Response to Treatment Despite Negative Test

Clinical response can guide diagnosis. When testing is inconclusive, improvement with treatment may support the diagnosis.

The patient was treated empirically with doxycycline for 14 days.

Within one week, the rash improved significantly without progression of symptoms.

This supports early treatment when suspicion is high.

Even Clinicians May Miss Atypical Rashes

Atypical rashes are frequently misidentified.

One study found:

• 25.7% misidentified uniformly red EM
• 43.6% misidentified disseminated EM
• 33.0% misidentified blue-purple EM

These errors contribute to delays described in our Lyme disease misdiagnosis guide.

Why This Matters

Atypical rash appearance combined with early negative testing can delay diagnosis.

• Lyme rashes are often not bull’s-eye in appearance
• Unusual colors, including purple, may occur
• Early testing may not confirm infection

Recognizing these patterns supports earlier diagnosis and better outcomes.

Start here: Lyme disease symptoms guide

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