Lyme Disease

Pathophysiology of Lyme Disease

Lyme disease is an

1) infection with Borrelia burgdorferi via tick bite
2) previous thinking held tick vector was Ixodes but transmission is now thought by some experts to be possible with additional tick species
3) occurs in stage I and stage II days to weeks after infection and in stage III months to years after infection (usually with preceding latency period

Signs and Symptoms

Stage I

1) characteristic expanding annular rash with central clearing (“bull’s eye or “target” rash) that occurs in only 40% of infections

Stage II

2) multiple secondary annular skin lesions
3) migratory musculoskeletal pain
4) heart block
5) shortness of breath
6) meningitis
7) headache
8) cranial and peripheral neuritis
9) abdominal pain
10) urinary dysuria and frequency

Stage III

11) encephalopathy
12) acrodermatitis
13) arthropathy
14) psychiatric disturbances (depression, hostile behavior)

Characteristic Test Findings


1) elevated sed rate
2) anti-Lyme antibodies (40%)
3) increased TNF and cytokines (organism is intensely proinflammatory)


4) brain lesions indistinguishable from multiple sclerosis on MRI

Histology and Gross Pathology

1) fastidious microaerophilic organism
2) grows best on Barbour, Stoenner, Kelly medium
3) microvasculitis

Associated Conditions

1) diagnosis of Lyme disease mandates testing for babesiosis, ehrlichiosis, anaplasmosis, and Bartonella
2) some experienced Lyme clinicians also test for mycoplasma, EBV, and herpes viruses
3) some patients experience Jarisch-Herxheimer reaction (worsening of symptoms) with introduction of antibiotics and other treatment modalities and at 28 days of treatment
4) clinical signs of hypothyroidism in setting of normal laboratory values (dubbed Wilson’s Syndrome by patients and some clinicians)
5) some clinicians feel coinfection with parasites and Rocky Mountain Spotted Fever is possible with Lyme infection


1) presence of immune complexes
2) “neurotoxin” release when organism dies has been postulated by some clinicians without firm laboratory confirmation

Inheritance and Epidemiology

1) Lyme disease occurs in all 50 states, Europe, and Asia
2) United States CDC estimates true incidence is 10 times number of cases that fit reporting criteria
3) tick vectors are infectious at all life stages (nypmh, larva, and adult)
4) transmission of microbes occurs when tick regurgitates on starting a blood meal (not with engorgement of tick 24 hours later
5) some clinicians believe that microbe can cross placenta and infect fetuses
6) microbe has been isolated in saliva, breast milk, semen, and contaminated blood products


1) treatment for Lyme disease  is highly controversial and the source of much rancor within the provider and patient communities
2) some physicians feel that the disease even in Stage III can be treated adequately with a relatively short course of antibiotics and remaining symptoms are “post-Lyme syndrome” unrelated to any existing microbes
3) other physicians believe continuing symptoms are a sign of continuing active infection and advocate years long use of antimicrobials and other modalities
4) many dozens of alternative medicine protocols have arisen with very little evidence based support other than anecdotal reports
5) phyisicans who believe in the chronic active infection hypothesis, amoxicillin, Augmentin, doxycycline, metronidazole (kills the cyst form supposedly), azithromycin, Ceftin, Rochephin, penicillin are among antibiotics used in combination over months to years
6) hyperbaric oxygen
7) “detox” stategies beyond the scope of this discussion

Tips for USMLE

Lyme disease is a clinical diagnosis and should NEVER be ruled out by absence of primary target rash, secondary erythema migrans, recognized tick bite, or negative serologic blood tests.

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