Lyme Disease

Topic updated on 08/23/16 6:57am
  • Systemic infection with Borrelia burgdorferi spirochete following bite of deer tick (Ixodes)  
  • Epidemiology
    • northeast, midwest, western US (areas with heavy deer population)  
      • Maryland to Maine (Ixodes scapularis)
      • Wisconsin, Minnesota  (Ixodes scapularis)
      • northern California (Ixodes pacificus)
    • less than 1% of Ixodes bites result in Lyme disease
    • peak incidence May to November
  • Body locations
    • affects skin, heart, CNS, joints, eyes
  • Organism
    • spirochete Borrelia burgdorferi  
    • survives in the absence of iron
    • takes 24 hours of tick attachment for transfer of the spirochete
      • regular "tick checks" may prevent infection
    • can survive intracellularly in fibroblast even with antibiotics in extracellular fluid
    • host
      • nymphs feed on white-footed mouse  
        • nymphs responsible for 90% of disease transmission
      • adults feed on white-tailed deer
    • reinfection is common (different serotype of B burgdorferi) but relapse is uncommon
  • Arthritis
    • susceptible patients have HLA DR4 or DR2, or HLA-DRB1*40 and antibodies to OspA and OspB proteins in joint fluid
    • immune mediated, persistent auto-immune inflammation even after organism is eradicated
  • Stage 1 (rash) - early localized 
    • 1 to 30 days after bite
    • erythema migrans
    • fatigue, myalgia, arthralgia, headache, fever, chills, neck stiffness
  • Stage 2 (neurologic) - early disseminated
    • weeks to months after bite
    • progresses to stage 2 in 50% of untreated disease
    • musculoskeletal and neurologic symptoms
      • migratory polyarthritis or monoarthritis, tendonitis, bursitis
      • CN VII neuropathy and meningitis
  • Stage 3 (arthritis) - chronic disseminated
    • months to years after bite
    • joints and neurologic symptoms
      • arthritis (usually the knee)
        • swelling disproportionate to tenderness
      • intermittent arthritis
      • chronic monoarthritis
    • acrodermatitis chronica atrophicans
  • Symptoms
    • tick bite in May through November
    • fever, headache, myalgia, arthralgia, fatigue
    • neurologic symptoms
      • headache, neck stiffness, encephalitis
      • facial CN VII palsy
        • bilateral in 50% (unlike Bell's palsy)
      • polyradiculoneuropathy
        • numbness, paresthesia, weakness, cramps
    • carditis (complete heart block)
    • acute joint pain
    • acute or chronic arthritis
  • Physical exam
    • erythema migrans ("bullseye rash") in 60-80% of patients  
      • expanding rash >5cm diameter 1 to 3 weeks after tick bite 
      • itching or burning
      • fades after 1 month
      • at axillary or gluteal folds, hairline, near elastic bands (bra strap or underwear)
    • acute, self limiting joint effusions 
      • knee and shoulder
      • recurrent
    • acrodermatitis chronica atrophicans  
      • "cigarette paper" skin
      • dorsum of hands, feet, knees, elbows
      • in older patients
  • Serum
    • WBC normal or elevated
    • ESR, CRP elevated
  • ELISA (sensitive)
    • 2 step test - if ELISA positive, proceed to Western blot (specific)
    • seroconversion takes weeks to become positive
    • prior Lyme disease might have persistently positive results
    • vaccination gives positive ELISA, negative Western blot
  • CSF (patients with polyradiculitis and CN VII neuropathy)
    • increased protein
    • lymphocytic pleocytosis
  • Synovial fluid
    • 10,000-25,000 WBC/mm3 
      • lower than baterial septic arthritis
    • PMN predominance
  • PCR
  • Culture on Barbour-Stoenner-Kelly medium
    • use skin edge punch biopsy from erythema migrans lesion
  • Bacterial septic arthritis
    • features that differentiate Lyme's diseae from bacterial septic arthritis include
      • ability to bear weight
      • normal serum WBC
      • lower synovial fluid WBC count
  • Non-operative
    • oral antibiotics for mild disease
      • indications
        • in endemic regions, if erythema migrans is present, start antibiotics without blood tests
      • medications
        • doxycycline (not in children <8 years) x 10 days
          • 28-30 days for arthritis, CN VII palsy or acrodermatitis
        • amoxicillin 
        • cefuroxime
    • IV antibiotics 
      • indications
        • for carditis, meningoencephalitis and arthritis
      • medications
        • IV ceftriaxone or cefotaxime
        • IV penicillin G
  • Operative
    • synovectomy
      • indications
        • chronic arthritis not responding to IV antibiotics


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Qbank (2 Questions)

(OBQ12.211) A 13-year-old boy presents to the emergency department in Rhode Island with knee pain for three days duration. It was atraumatic in onset. He has been afebrile. Upon physical examination, he is noted to have a tense, swollen knee and the skin lesion seen in Figure A. An oral course of antibiotics is selected as definitive management. What antibiotic would be most appropriate for this patient, and what is its primary mechanism of action? Topic Review Topic
FIGURES: A          

1. Doxycycline, Inhibits the 50s ribosomal subunit
2. Doxycycline, Inhibits the 30s ribosomal subunit
3. Cephalexin, Blocks cell wall synthesis
4. Cephalexin, Folic acid inhibitor
5. Rifampin, RNA synthesis inhibitor

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