Differential Diagnosis for Positive Lyme Antibody Screen
The patient's laboratory results indicate a positive Lyme antibody screen, with positive Lyme IgG confirmation and negative Lyme IgM confirmation. Based on these results, the following differential diagnosis is considered:
- Single most likely diagnosis:
- Lyme disease: The patient's positive Lyme IgG confirmation suggests a recent or remote past infection with B. burgdorferi, which is consistent with Lyme disease. The presence of IgG-class antibodies indicates a mature immune response, which can persist for months to years after resolution of the infection.
- Other Likely diagnoses:
- Southern Tick-Associated Rash Illness (STARI): Although the patient's laboratory results are consistent with Lyme disease, STARI is a similar condition that can present with a rash and other symptoms. However, STARI is typically associated with a different tick species and does not test positive for Lyme antibodies.
- Ehrlichiosis/Anaplasmosis: These tick-borne illnesses can present with similar symptoms to Lyme disease, including fever, headache, and rash. However, they are caused by different bacteria and require different laboratory tests for diagnosis.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
- Rocky Mountain Spotted Fever (RMSF): Although RMSF is a less common tick-borne illness, it can be life-threatening if left untreated. The patient's symptoms and laboratory results do not specifically suggest RMSF, but it is essential to consider this diagnosis due to its potential severity.
- Babesiosis: This parasitic infection can be transmitted through tick bites and can cause severe anemia, particularly in immunocompromised individuals. Although the patient's laboratory results do not suggest babesiosis, it is crucial to consider this diagnosis due to its potential severity.
- Rare diagnoses:
- Relapsing Fever: This rare tick-borne illness is caused by a different species of Borrelia and can present with recurring episodes of fever and other symptoms. However, it is relatively rare and typically requires specific laboratory tests for diagnosis.
- Tick-Borne Relapsing Fever (TBRF): Similar to relapsing fever, TBRF is a rare tick-borne illness that can cause recurring episodes of fever and other symptoms. It is essential to consider this diagnosis in patients with a history of tick exposure and recurring symptoms.