Differential Diagnosis for 2 Tick Bites with Red Bullseye
- Single most likely diagnosis
- Lyme disease: This is the most likely diagnosis due to the classic presentation of a red bullseye rash (erythema migrans) following a tick bite, which is a hallmark symptom of Lyme disease.
- Other Likely diagnoses
- Southern tick-associated rash illness (STARI): This condition presents with a similar rash to Lyme disease but is caused by a different tick species and does not progress to the same systemic symptoms.
- Tick-borne relapsing fever: While less common, this disease can also present with a rash and is transmitted by ticks, although it typically involves a different species and has a distinct fever pattern.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Rocky Mountain spotted fever (RMSF): Although the rash in RMSF is typically more widespread and petechial, early stages can resemble a bullseye rash, and missing this diagnosis can be fatal due to its rapid progression and severity.
- Tularemia: This bacterial infection can be transmitted by tick bites and, in its ulceroglandular form, might initially present with a skin lesion that could be mistaken for a bullseye rash, making it crucial not to miss due to its potential severity.
- Rare diagnoses
- Borrelia miyamotoi disease: A rare tick-borne illness that can cause fever, headache, and a rash, although the rash is not typically described as a bullseye.
- Ehrlichiosis: While primarily causing fever and systemic symptoms, some forms of ehrlichiosis can present with a rash, although this is less common and not typically a bullseye pattern.