What is the differential diagnosis and recommended management for a 68-year-old male with a history of stroke and Lyme (Lyme disease) disease, presenting 14 days post tick bite with two ticks, one still embedded, and symptoms of mild fever, malaise, and increased unsteadiness in gait?

Differential Diagnosis for 68-year-old Male with History of Stroke and Lyme

Single Most Likely Diagnosis

• Lyme Disease: Given the patient's history of Lyme disease and the recent tick bite with one tick still embedded, Lyme disease is the most likely diagnosis. The patient's symptoms of mild fever, malaise, and increased unsteadiness in gait are consistent with early disseminated Lyme disease, particularly given the 14-day post-tick bite timeline.

Other Likely Diagnoses

• Southern Tick-Associated Rash Illness (STARI): Although less common, STARI is a consideration given the tick bite and the patient's symptoms. However, the presence of systemic symptoms like fever and malaise makes Lyme disease more likely.
• Ehrlichiosis/Anaplasmosis: These tick-borne illnesses can present with similar symptoms, including fever and malaise, and should be considered in the differential diagnosis, especially given the patient's recent tick bite.
• Rocky Mountain Spotted Fever (RMSF): Although less common in areas where Lyme disease is prevalent, RMSF is a tick-borne illness that can present with fever, malaise, and neurological symptoms, making it a consideration in this patient's differential diagnosis.

Do Not Miss Diagnoses

• Tick-Borne Relapsing Fever (TBRF): This diagnosis is critical not to miss due to its potential for severe neurological complications if left untreated. The patient's increased unsteadiness in gait could be indicative of neurological involvement.
• Babesiosis: A parasitic infection transmitted by ticks, babesiosis can cause severe anemia, particularly in older adults or those with compromised immune systems. Given the patient's age and history of stroke, this diagnosis is crucial not to miss.
• Meningitis/Encephalitis: Given the patient's history of stroke and current symptoms of increased unsteadiness in gait, it is essential to consider meningitis or encephalitis, especially if caused by a tick-borne pathogen. These conditions require immediate medical attention.

Rare Diagnoses

• Powassan Virus Disease: A rare but potentially severe tick-borne viral disease that can cause encephalitis or meningitis. The patient's neurological symptoms could be indicative of this rare infection.
• Tick-Borne Viral Diseases (e.g., Colorado Tick Fever): Other viral diseases transmitted by ticks are rare but should be considered, especially if the patient has been in areas where these diseases are endemic.

Recommendations

• Immediate removal of the embedded tick.
• Blood tests for Lyme disease, Ehrlichiosis/Anaplasmosis, and Babesiosis.
• Consideration of empirical antibiotic treatment for Lyme disease given the high suspicion based on clinical presentation and history.
• Neurological evaluation to assess for any potential complications or to rule out other neurological conditions.
• Monitoring for signs of more severe tick-borne illnesses, including meningitis/encephalitis and TBRF.