Differential Diagnosis for Tick Bite with Bullseye Redness
- Single most likely diagnosis
- Lyme disease: This is the most likely diagnosis given the classic presentation of a bullseye rash (erythema migrans) after a tick bite. The rash is often accompanied by other symptoms, but it's not uncommon for patients to be asymptomatic aside from the rash.
- Other Likely diagnoses
- Southern tick-associated rash illness (STARI): This condition presents similarly to Lyme disease with a bullseye rash but is caused by a different tick species and does not progress to the same systemic symptoms as Lyme disease.
- Tick bite granuloma: This is a localized reaction to the tick bite that can cause a rash, but it does not have the distinctive bullseye pattern of Lyme disease.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Rocky Mountain spotted fever (RMSF): Although less common and not typically presenting with a bullseye rash, RMSF can start with a rash and is a life-threatening condition if not treated promptly. It's crucial to consider this diagnosis, especially if the patient develops fever, headache, or other systemic symptoms.
- Tularemia: This bacterial infection can be transmitted by tick bites and, while rare, can be severe and life-threatening if not treated.
- Rare diagnoses
- Babesiosis: A parasitic infection transmitted by ticks that can cause a range of symptoms from mild to severe, including hemolytic anemia. It's more common in certain geographic areas and typically presents with systemic symptoms rather than a localized rash.
- Ehrlichiosis/Anaplasmosis: These are bacterial infections transmitted by ticks that can cause fever, headache, and other systemic symptoms. While they can present with a rash, it's not typically a bullseye pattern.