Lyme Disease

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Presentation :

• 3 Major Phases of Disease:
  • Early Localized (≤4 wk):
    • EM at site of tick attachment, variably with fever, lymphadenopathy, myalgia
    • Erythema Migrans: usually painless, nonpruritic, and circumferentially enlarging
      
    • Local cutaneous reactions resulting from hypersensitivity to tick saliva may resemble EM but tend to occur earlier, are pruritic, and do not enlarge significantly after onset.
  • Early disseminated (2 wk-6 mo): Without treatment, hematogenous dissemination occurs in up to 60% of patients.
    • Constitutional: flu-like syndrome
    • Cardiac: heart block, myocarditis
    • Dermatologic: Multiple sites of EM at sites distant from the original tick attachment
    • Neurologic: cranial neuropathies, meningitis, radiculitis, mononeuritis multiplex, spinal cord or brain parenchymal inflammation
  • Late disseminated (≥6 mo):
    • Arthritis: Approximately 60% of untreated patients with Lyme disease develop a monoarticular or oligoarticular inflammatory arthritis as a late complication
    • Neurologic: peripheral neuropathy, encephalopathy
    • Dermatologic: acrodermatitis chronica atrophicans

Pathophysiology :

• Transmitted by Ixodes scapularis (Blacklegged Deer Tick)
• The causative spirochete, Borrelia burgdorferi, is transmitted intradermally when a tick ingests a blood meal.
• Transmission typically occurs after at least 36 hours

Diagnostic Testing:

• Patients with EM and a compatible exposure history do not require confirmatory laboratory testing before treatment
• Early disseminated Lyme disease should be evaluated using ELISA followed by confirmatory testing

Treatment :

• Prophylaxis:
  • In highly select situations, prophylaxis with a single dose (200 mg) of doxycycline may decrease the risk of Lyme disease after a tick bite. Prophylactic doxycycline is only recommended. Otherwise, observation is recommended, with treatment given if suggestive symptoms develop.
    1. the tick is reliably identified as a blacklegged deer tick
    2. attachment lasts 36 hours or longer
    3. antibiotics can be started less than 72 hours after tick removal
    4. prevalence of B. burgdorferi infection of ticks in the region exceeds 20%.
• Early Localized:
  • Doxycycline, 100 mg PO BID × 10 d (first-line therapy)
  • Amoxicillin, 500 mg PO TID × 14 d
  • Cefuroxime axetil, 500 mg PO BID × 14 d
• Early Disseminated:
  • Cardiac:
    • Hospitalized patients (first-degree block with PR interval ≥300 msec, higher degree heart block, other arrhythmias, myopericarditis): initial IV ceftriaxone with transition to oral for total of 14-21 days
    • Outpatients (first-degree AV block with PR interval <300 msec): oral treatment same as for early localized disease × 14-21 d
  • Meningoencephalitis: IV penicillin G, IV cefotaxime, or IV ceftriaxone or oral doxycycline × 14-21 d (IV antibiotics preferred for spinal or brain parenchymal involvement)
  • Other manifestations (including facial palsy): oral treatment the same as for early localized disease × 14-21 d
• Late Disseminated:
  • Initial rheumatologic treatment: same as for early localized but × 28 d
  • Arthritis unresponsive to initial treatment: IV ceftriaxone 2-4 weeks

Prognosis:

Lyme Disease Distribution

References:

• MKSAP