LYME DISEASE

 

Etiology:

  1. Spirochete infection (Borrelia burgdorferi) 2ry to deer tick bite (Ixodes). Small mammals serve as hosts for the tick, with deer being an important host for the adult tick.  The tick also attaches to vegetation/bushes and infects humans.  It has been reported throughout the US, but most cases are still seen in the New England and mid-Atlantic regions.
  2. The tick must be in contact for at least 24 hrs to transmit the infection.

S & S:

  1. Incubation is 1-36 days (10 days median).
     
  2. Malaise, fatigue, fever, arthralgia, headache, nausea, abdominal pain can all be present.
     
  3. The bite is asymptomatic but the characteristic erythema chronicum migrans (ECM) lesion may cause itching.  If tick is removed in less than 24 hours transmission is less likely to occur.  Only 10% of the tick bites will transmit the disease.  Less than 75% of pts develop ECM.
     
  4. Lyme is classified into "stages" (but note that not all stages need to appear and stages may overlap):

 

Stage I

  1. ECM = a macule that enlarges and assumes annular form with central  clearing.  Trunk, axilla and inguinal areas are the common sites.  Appears on average on 7-10th day with a range of 3-31 days.
     
  2. Regional adenopathy, sore throat and some constitutional S & S.

 

Stage II (may occur days to a few weeks after infection)

 

  1. Secondary annular lesions = 20% of pts develop these small ECM-like lesions that are multiple and can occur anywhere except palms/soles.
     
  2. Lymphocytoma cutis = usually is a single painless nodule located on ear lobe, nipple or scrotum.
     
  3. Malar rash, erythema.
     
  4. Joint pains (arthralgias) occur in 60% of cases in 4-20 weeks, malaise, adenopathy.
     
  5. Neurological findings occur in 15% of cases. May manifest as meningitis, Bell's (especially bilateral), neuritis.  Occurs in average at 4 weeks after ECM.
     
  6. Cardiac manifestations such as AV blocks (be suspicious of Lyme when young pt has an AVB), arrhythmias, pericarditis.  Occur in 10% of cases at 4 weeks after ECM.
  7. Mucous membranes involved with conjunctivitis, red oropharynx.

 

Stage III

 

  1. Occurs in average 4-6 weeks after ECM, but like other stages can take weeks to years.
     
  2. Arthritis, neurological manifestations and malaise may become chronic.
     
  3. Acrodermatitis chronica atrophicans =a late manifestation of Lyme that initially presents as redness with edema of lower extremities and slowly progresses to atrophy.

 

DX:

  1. History and clinical evidence of dermatologic findings
     
  2. Lyme titers: IgM detected after 6 weeks followed by IgG. When only ECM is present, a positive serology is present in only 50% of the patients.
     
  3. Biopsy of  EM shows spirochetes in 40% of cases.

Treatment:

  1. Stage I : Doxycycline 100mg BID or, if pregnant/lactating, Amoxicillin 500mg TID both x 14-21days.  Other alternatives include cefuroxime axetil 500mg Bid x21 days and clarithromycin 500mg BID x14-21 days.
     
  2. Stage II or III (carditis, neuro and arthritis) is usually treated with Ceftriaxone 2g IV QD x 14- 21 days, but can be treated with oral regimens (e.g. Doxycycline 100mg BID x21-28 days) if clinical picture is mild.

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