Borrelia burgdorferi

Snapshot

• A 30-year-old male presents to the urgent care clinic for a round rash on his thigh. He reports that he noticed this rash 3 days ago while showering and has since expanded in size. He denies any pain, itching, or blistering from this rash. Two weeks ago, he had gone hiking in Connecticut while visiting relatives but denies pulling off any ticks, though he admits he did not thoroughly check after his hike. He denies any fevers or chills. On physical exam, there is an annular erythematous rash with central clearing on the left thigh with a diameter of 7 cm. He is given a course of antibiotics for presumed Lyme disease.

Introduction

• Classification 
  • Borrelia burgdorferi
    • a spirochete (spiral-shaped bacteria)
      • does not gram-stain well due to thin cell walls
    • transmission
      • Ixodes tick
    • clinical syndrome
      • Lyme disease, a tick-borne illness characterized by 3 stages (see below)
• Epidemiology
  • incidence
    • northeast and upper midwest US
  • risk factors
    • tick bite
    • hiking and other outdoor activities
• Associated conditions
  • ehrlichiosis 
    • same tick vector
  • babesiosis 
    • same tick vector
• Prognosis
  • erythema migrans may resolve without treatment
• excellent prognosis with treatment

Presentation

• Symptoms
  • early localized stage
    • erythema migrans (within 1 month of tick bite) 
      • expanding area of round erythema with central clearing, resulting in the classic targetoid lesion
        • classic “bulls-eye” rash
      • flat or raised
      • not tender or pruritic
    • systemic symptoms
      • fever
      • myalgia
      • arthralgia
      • headache
      • fatigue
  • early disseminated stage
    • multiple erythema migrans
    • neurologic symptoms
      • facial nerve palsy, typically bilateral
      • meningitis
      • mononeuritis multiplex
    • Lyme carditis
      • third-degree (complete) atrioventricular block
      • myopericarditis
  • late stage
    • arthritis involving knees, classically
    • encephalopathy
• polyneuropathy

Studies

• Labs
  • serologic detection of immunoglobulins using enzyme-linked immunosorbent assay (ELISA)
• Making the diagnosis
• based on clinical presentation

Differential

• Erythema multiforme 
  • distinguishing factors
    • also presents with an annular rash though often presents with numerous annular lesions that are smaller and may show blistering
    • not associated with a tick bite
• often associated with viral infections or medications

Treatment

• Medical
  • doxycycline or amoxicillin 
    • indications
      • erythema migrans
      • Lyme arthritis
  • ceftriaxone
    • indications     
      • neurologic Lyme disease
      • Lyme carditis
      • other disseminated Lyme disease
  • macrolides
    • indication
• second-line in those who are allergic to first-line medications

Complications

• Chronic arthritis
• Post-Lyme syndrome
  • although there is no biologic evidence or accepted definition for symptomatic chronic Lyme disease after completion of initial antibiotics, many patients report fatigue