|
https://upload.orthobullets.com/topic/9052/images/erythema migrans.jpg
https://upload.orthobullets.com/topic/9052/images/ixodes.jpg
https://upload.orthobullets.com/topic/9052/images/map.jpg
https://upload.orthobullets.com/topic/9052/images/borrelia.jpg
https://upload.orthobullets.com/topic/9052/images/atrophica.jpg
Introduction
  • Systemic infection with spirocheteBorrelia burgdorferi transmitted by the bite of infected deer tick (Ixodes)  
  • Epidemiology
    • incidence
      • most common tick-borne illness in the US
      • 19,931 cases in 2006
      • most cases occur in June, July, and August
    • demographics
      • bimodal age distribution
        • children 5-9 (8.6 cases/100,000)
        • adults 55-59 (7.8 cases/100,00)
      • geographic locations
        • northeast, midwest, western US (areas with heavy deer population)  
        • Maryland to Maine (Ixodes scapularis)
        • Great Lakes region  (Ixodes scapularis)
        • Pacific Northwest (Ixodes pacificus)
  • Pathophysiology
    • mechanism of transmission
      • zoonotic - transmitted from nonhuman animals to humans
        • mice, squirrels, shrews, and other small mammals are carriers of B burgdorferi
        • Ixodes tick feeds on these small animals and spirochete is carried in its gut
        • humans become infected when bacteria is injected into the skin as ticks attach to feed 
          • transmission takes 48-72 hours
    • pathophysiology
      • caused by B burgdorferi
      • tick saliva with spirochete disrupt local immune mechanisms
      • create a protective invironment and the bacteria replicate
      • spirochetes multiply and expand within the dermis, causing erythema migrans
        • rash caused by the host inflammatory response
      • the spirochete then undergoes hematogenous dissemination to multiple sites
        • skin
        • central nervous system
        • joints
          • induces an inflammatory response
            • synovial hypertrophy
            • vascular proliferation
            • infiltration of mononuclear cells
            • immune complexes accumulate in synovial fluid
    • pathobiology
      • B burgdorferi induces chondrocytes to produce matrix metalloproteinases
        • causes degradation of extracellular matrix proteins, collagen, and proteoglycans
        • may contribute to cartilage damage
Classification
  • Stage 1 (rash) - early localized 
    • 1 to 30 days after bite
    • erythema migrans (bull's-eye rash) is hallmark
    • rash may be found on head, neck, arms, legs, back, abdomen, axilla, groin, and chest
    • flu-like symptoms
      • fatigue
      • headache
      • malaise
  • Stage 2 (neurologic and cardiac) - early disseminated
    • weeks to months after bite
    • progresses to stage 2 in 15-20% of untreated patients
    • neurologic symptoms
      • CN VI palsy
      • CN VII palsy 
      • lymphocytic meningitis
      • migratory polyarthritis or monoarthritis, tendonitis, bursitis
    • Lyme carditis relatively rare
      • may have a cardiac conduction abnormality
      • symptoms
        • syncope
        • fatigue
        • dizziness
        • shortness of breath
        • palpitation
    • prognosis good with complete resolution following treatment
  • Stage 3 (arthritis) - late
    • months to years after bite
    • occurs in 60% of untreated patients
    • arthritis (usually the knee)
      • swelling disproportionate to tenderness
      • intermittent arthritis
      • chronic monoarthritis
    • acrodermatitis chronica atrophicans
Presentation
  • History
    • tick bite in May through November
  • Symptoms
    • 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
Studies
  • Serum labs
    • WBC normal or elevated
    • ESR, CRP elevated
  • ELISA (sensitive, not specific)
    • 2 steps
      • 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
  • Joint aspiration / Synovial fluid
    • 10,000-25,000 WBC/mm3 
      • lower than baterial septic arthritis
    • PMN predominance
  • Skin biopsy culture
    • Culture on Barbour-Stoenner-Kelly medium
    • use skin edge punch biopsy from erythema migrans lesion
  • PCR
Differential
  • 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
Treatment
  • Non-operative
    • oral antibiotics for mild disease
      • indications
        • in endemic regions, if erythema migrans is present, start antibiotics without blood tests
      • medications
        • adults
          • doxycycline (not in children <8 years) x 10 days
          • amoxicillin 
          • cefuroxime
        • children (<8-years-old)
          • amoxicillin
          • cefuroxime
    • IV antibiotics 
      • indications
        • arthritis and neurologic involvement                         
        • patients whose symptoms are unchanged after oral therapy
      • medications
        • IV ceftriaxone or cefotaxime
        • IV penicillin G
  • Operative
    • synovectomy
      • indications
        • chronic arthritis not responding to IV antibiotics
Complications
  • May have a slightly increased incidence of persistent joint swelling despite therapy
  • Chronic Lyme disease
    • disabling musculoskeletal pain
    • neurocognitive symptoms
    • fatigue
  • Chronic arthritis rare
 

Please rate topic.

Average 4.5 of 6 Ratings

Questions (6)
EVIDENCE & REFERENCES (9)
Topic COMMENTS (1)
Private Note