Differential Diagnosis for Tick Bite
- Single most likely diagnosis
- Localized tick bite reaction: This is the most likely diagnosis given the patient's history of removing a tick 2 weeks ago and continued symptoms at the bite site. The reaction can cause persistent redness, swelling, and itching.
- Other Likely diagnoses
- Lyme disease: Although the patient has had other bites since, it's possible that the removed tick was infected with Borrelia burgdorferi, causing Lyme disease. Early symptoms can include a rash at the bite site.
- Southern tick-associated rash illness (STARI): This condition, caused by the lone star tick, can cause a rash similar to Lyme disease, but it's typically smaller and doesn't expand as much.
- Ehrlichiosis or Anaplasmosis: These tick-borne illnesses can cause symptoms like fever, headache, and fatigue, but a rash at the bite site can also occur.
- Do Not Miss
- Rocky Mountain spotted fever (RMSF): This potentially life-threatening disease, caused by Rickettsia rickettsii, can cause a rash, fever, and headache. It's essential to consider RMSF, especially if the patient has severe symptoms or exposure to ticks in endemic areas.
- Tularemia: This bacterial infection, caused by Francisella tularensis, can cause a painful ulcer at the bite site, followed by fever, chills, and swollen lymph nodes.
- Rare diagnoses
- Babesiosis: A parasitic infection caused by Babesia microti, which can cause symptoms like fever, fatigue, and anemia. It's typically seen in immunocompromised patients or those with a history of splenectomy.
- Tick-borne relapsing fever (TBRF): A bacterial infection caused by Borrelia species, which can cause recurring episodes of fever, headache, and muscle pain.
- Powassan virus disease: A viral infection that can cause symptoms like fever, headache, and encephalitis. It's relatively rare but can be severe.