Lyme disease
Lyme disease is a tick-borne spirochetal infection caused by Borrelia burgdorferi that progresses from erythema migrans through early disseminated cardiac and neurologic disease to late arthritis, diagnosed clinically when erythema migrans is present and otherwise by two-tiered serology, and treated with staged doxycycline, amoxicillin, or cefuroxime regimens.
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What this article covers
- Overview
Tick-borne spirochetal infection: Lyme disease is caused by the spirochete Borrelia burgdorferi, transmitted intradermally when an infected Ixodes scapularis (blacklegged deer) tick feeds, and is the…
- Epidemiology
Concentrated in Ixodes scapularis-endemic regions: the northeastern, mid-Atlantic, and upper Midwest United States account for over 95% of reported cases.
- Risk factors
Outdoor exposure in an endemic area: hiking, gardening, or occupational activity in wooded or high-grass habitat where Ixodes scapularis is established.
- Pathophysiology
Intradermal inoculation: Borrelia burgdorferi is transmitted into the skin during a blood meal by an infected tick; local spirochete replication produces the expanding erythema migrans lesion at the attachment site.
- Clinical features
Erythema migrans (hallmark, early localized, within 4 weeks of the bite): a red, annular, expanding skin lesion, often with central clearing, in 70-80% of infected persons at or near the attachment…
- Differential diagnosis
Southern tick-associated rash illness (STARI): an erythema migrans-identical lesion, but follows a Lone Star tick (Amblyomma americanum) bite in the southeastern, south-central, and eastern United…
- Diagnosis
Erythema migrans with a compatible exposure history is a clinical diagnosis; no confirmatory testing is required.
- Management
Early localized disease (EM present, no disseminated features): start one oral regimen below; the first also treats incubating Anaplasma phagocytophilum coinfection.
- Complications
Complete heart block: the most acute complication of Lyme carditis, can progress rapidly despite treatment, requiring hospitalization and monitoring in symptomatic or high-grade cases.
- Prognosis
Excellent with prompt stage-appropriate treatment: most patients treated at the early localized or early disseminated stage recover fully.
- Prevention
Avoid tick attachment: permethrin-treated clothing, skin repellents, and tick checks after time in wooded or high-grass habitat in an endemic area.
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