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Updated: Apr 26 2023

Lyme Disease

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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/borrelia.jpg
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  • summary
    • Lyme Disease is a systemic infection caused by tick-born B. burgdorferi which usually presents with flu-like symptoms, a characteristic rash, and occasionally acute joint effusions.
    • Diagnosis is confirmed by a history of travel to a tick-heavy regions, presence of erythema migrans rash, and a positive lyme titers on an ELISA test.
    • Treatment is usually oral doxycycline for acute or mild disease.
  • 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)
  • Etiology
    • 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 environment 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
    • Persistent joint pain
      • may have a slightly increased incidence of persistent joint swelling despite therapy
    • Chronic Lyme disease
      • disabling musculoskeletal pain
      • neurocognitive symptoms
      • fatigue
    • Chronic arthritis
      • rare
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