Lyme disease (Lyme borreliosis) is a multisystem infection caused by the tick-transmitted spirochete Borrelia burgdorferi. It is the most common vector-borne disease in the United States. Infection rates in ticks vary between 15% and 65% in endemic regions, but transmission requires an infected tick to feed on the human host for more than 24 hours.

Clinical Concept: Following a tick bite, a single oral 200-mg dose of doxycycline effectively reduces the risk of developing Lyme disease if the tick is engorged and the patient lives in or visited a Lyme-endemic area.

1. Clinical Presentation by Stage

Lyme disease typically progresses through three distinct clinical stages:

• Stage 1 (Early Localized Disease): Mild flu-like illness presenting with a classic single annular lesion featuring central clearing (erythema migrans). The rash is rarely pruritic or painful, and symptoms can self-resolve in 3 to 4 weeks without treatment.
• Stage 2 (Early Disseminated Infection): Occurs months later; the classic rash may reappear with multiple lesions, accompanied by arthralgias, myalgia, headache, and fatigue. Less common manifestations include cardiac involvement (e.g., heart block) and neurological features such as acute facial nerve paralysis (Bell’s palsy) or aseptic meningitis.
• Stage 3 (Late Persistent Infection): Begins approximately 1 year after initial infection. Musculoskeletal symptoms persist, ranging from joint pain without objective findings to frank arthritis with joint damage. Neuropsychiatric manifestations can emerge, including memory impairment, depression, and neuropathy.

2. Diagnostic Approach

Diagnosis relies on clinical evaluation paired with a two-tier serological testing protocol to avoid false-positive and false-negative errors:

• Screening Assay: Initial screening with an enzyme-linked immunosorbent assay (ELISA).
• Confirmatory Testing: Follow-up testing with a Western blot assay for IgM and IgG antibodies.
• Serological Kinetics: IgM antibodies decline to low levels within 4 to 6 months of illness. IgG antibodies appear 6 to 8 weeks after symptom onset and often persist at low levels despite successful treatment.
• Laboratory Note: Complete blood count (CBC) is typically normal and not diagnostically helpful. Astute interpretation is essential to prevent both overdiagnosis and underdiagnosis.

3. Treatment & Prophylaxis Strategies

Antimicrobial selection and duration depend on disease stage and clinical complexity:

Prognosis & Prevention: Most adult patients recover fully within weeks of initiating appropriate antimicrobial therapy, though late relapses can occur. Preventive measures include using insect repellents, wearing protective clothing (long sleeves and pants), avoiding tick-infested areas, and conducting routine post-exposure skin checks with prompt tick removal.

References

1. Barbour A. Symptoms, diagnosis and treatment of Lyme disease. American Lyme Disease Foundation.
2. Centers for Disease Control and Prevention. Lyme disease.
3. Gilbert DN, Chambers HF, Eliopoulos GM, Saag MS, Pavia AT. The Sanford Guide to Antimicrobial Therapy. 50th ed. Sperryville, VA: Antimicrobial Therapy, Inc.; 2020:60.