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Difficulty: EasyInfectious Diseases

A 3434-year-old woman presents to the clinic for evaluation of a skin rash. She noticed the rash on her right posterior thigh 44 days ago, and it has steadily increased in size. She recently returned from a camping trip in Maine. The patient reports mild fatigue and muscle aches but denies fever, joint swelling, or shortness of breath. Her temperature is 37.1∘C37.1^\circ\text{C} (98.8∘F98.8^\circ\text{F}), blood pressure is 120/78 mm Hg120/78\text{ mm Hg}, and pulse is 76/min76\text{/min}. Physical examination reveals a 10-cm10\text{-cm}, annular, erythematous plaque with a central area of clearing on the right posterior thigh. The remainder of the examination is unremarkable. Which of the following is the most appropriate next step in management?

  1. Prescribe oral doxycyclineAnswer
  2. B
    Perform serologic testing for Borrelia burgdorferi
  3. C
    Prescribe intravenous ceftriaxone
  4. D
    Prescribe oral cephalexin
  5. E
    Prescribe topical hydrocortisone

Answer

Prescribe oral doxycycline
The correct action is to prescribe oral doxycycline. This patient presents with a classic erythema migrans rash (annular, erythematous plaque with central clearing) and a history of recent travel to a Lyme-endemic area, which is diagnostic for early localized Lyme disease. In early localized disease, empiric treatment with an oral antibiotic (such as doxycycline, amoxicillin, or cefuroxime) should be initiated immediately based entirely on clinical findings.

Step-by-Step Solution

1
Identify the primary clinical finding and its significance.
The patient has a large, expanding annular erythematous plaque with central clearing (erythema migrans) after visiting a Lyme-endemic area.
Erythema migrans is the hallmark physical finding of early localized Lyme disease.
2
Determine the appropriate diagnostic approach.
Diagnosis is made clinically based on the characteristic rash; serologic testing is unnecessary at this stage.
Antibodies to Borrelia burgdorferi often take weeks to develop, so serology has low sensitivity early in the disease course and can yield false-negative results.
3
Select the optimal management strategy.
Initiate empiric oral antibiotic therapy.
Oral doxycycline is the first-line treatment for early localized Lyme disease in non-pregnant adults.

Key Concept

Diagnosis and management of early localized Lyme disease
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Topics

Infectious Diseases

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