Differential Diagnosis for Tick-Borne Illness with Elevated Liver Function Tests and Rash

• Single Most Likely Diagnosis
  • Southern Tick-Associated Rash Illness (STARI): Although STARI is characterized by a rash and is tick-borne, it typically does not cause elevated liver function tests. However, given the combination of symptoms, Lyme disease is more likely as it can cause both a rash (erythema migrans) and elevated liver enzymes in some cases.
• Other Likely Diagnoses
  • Ehrlichiosis/Anaplasmosis: These are tick-borne illnesses that can cause elevated liver function tests and sometimes a rash. They are more likely to cause systemic symptoms such as fever and headache but can be considered with the given symptoms.
  • Rocky Mountain Spotted Fever (RMSF): This illness can cause a rash and elevated liver enzymes. It's a serious disease with a high mortality rate if not treated promptly, making it an important consideration.
• Do Not Miss Diagnoses
  • Babesiosis: Although primarily known for causing hemolytic anemia, babesiosis can lead to elevated liver enzymes due to hemolysis and should not be missed due to its potential severity, especially in asplenic or immunocompromised patients.
  • Tick-Borne Relapsing Fever (TBRF): This disease can cause a variety of symptoms including fever, headache, and rash, and while less common, it's critical not to miss due to its potential for severe outcomes if untreated.
• Rare Diagnoses
  • Southern Tick-Associated Rash Illness (STARI): As mentioned, while it's a tick-borne illness with a rash, it's less commonly associated with elevated liver function tests, making it a less likely but still possible diagnosis.
  • Powassan Virus Disease: A rare tick-borne viral disease that can cause encephalitis and meningitis, and while it might not primarily present with rash and elevated liver function tests, its severity warrants consideration in the differential diagnosis of tick-borne illnesses.