Updated: 12/19/2019

Lyme Disease

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Topic
Snapshot
  • A 16-year-old boy presents to his primary care physician with fatigue, malaise, and a rash. His symptoms began approximately 1 week ago and have progressively worsened. He said he recently hiked in northern Connecticut but is unsure if he was bitten by a tick. On physical exam, there is an erythematous and slightly raised lesion that appears "target-like" on the right thigh. He is given oral doxycycline.
Introduction
  • Definition
    • a tick-borne illness characterized by 3 stages
      • early localized stage (within 1 month of the tick bite)
        • erythema migrans
      • early disseminated stage
        • multiple erythema migrans
        • neurological symptoms (e.g., facial nerve palsy, meningitis, and mononeuritis multiplex)
        • cardiac symptoms (e.g., carditis)
      • late stage
        • arthritis
        • encephalopathy or polyneuropathy
  • Epidemiology
    • incidence
      • most cases in the northeast and upper midwest
  • Etiology
    • Borrelia burgdorferi, a spirochete transmitted by the Ixodes tick
      • this tick is also a vector for
        • Anaplasma spp.
        • Babesia microti
  • Prognosis
    • the rash typically self-resolves without treatment
    • untreated Lyme disease can result in arthritis
    • excellent prognosis with early antibiotic treatment 
Presentation
  • Symptoms 
    • early localized stage
      • erythema migrans (7-14 days post-tick bite)
        • round erythema that expands and can result in the classic target lesion
        • may be accompanied by systemic symptoms such as
          • fevers
          • myalgias
          • arthralgias
          • headache
          • fatigue
    • early disseminated stage 
      • multiple erythema migrans
      • neurological symptoms (e.g., facial nerve palsy, meningitis, and mononeuritis multiplex)
      • lyme carditis
        • may present as an atrioventricular block and/or myopericarditis
    • late stage
      • arthritis
        • the knees are classically involved
      • encephalopathy or polyneuropathy
Differential Diagnosis
  • Ehrlichiosis 
    • fever, malaise, aches, without a rash
    • leukopenia, thrombocytopenia and elevated aminotransferases
Studies
  • Making the diagnosis
    • this is a clinical diagnosis
  • Cerebrospinal fluid analysis when there is central nervous system involvement
  • Synovial fluid analysis when arthritis is suspected
  • Serologic studies
    • performed to support the clinical diagnosis 
Treatment
  • Medical
    • doxycycline or amoxicillin  
      • indication
        • erythema migrans
        • Lyme arthritis
      • macrolides can be used in patients who are allergic to doxycycline, ceftriaxone, and cefuroxime
    • ceftriaxone
      • indication
        • neurologic Lyme disease
        • Lyme carditis

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