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  1. Collette McCourt, specialist trainee year 5, dermatology,
  2. Cliona Feighery, specialist registrar in dermatology,
  3. Kevin McKenna, consultant dermatologist
  1. 1Belfast City Hospital, Belfast BT12 6BA, UK
  1. Correspondence to: C McCourt collmccourt{at}hotmail.com

A 65 year old woman presented with a six week history of an asymptomatic eruption on her thighs. She described a “50 pence” sized area of redness on her right thigh that had gradually expanded in size. Within two weeks of the initial lesion, a second expanding area of erythema developed on the left thigh. She was systemically well, with no fevers, lethargy, or arthralgia. Her only medical history of note was breast carcinoma, which had been treated with a mastectomy, and she had been taking oral tamoxifen for six months. When the eruption first occurred in the summer, she was on holiday in the Limousin region of France (a woodland area), although she did not remember having tick bites. On examination, three 15-20 cm non-scaly patches with a macular erythematous edge were noted on her thighs (fig 1).

Questions

  • 1 What is the most likely diagnosis?

  • 2 What other systems may be affected by this disease?

  • 3 How is it treated?

Answers

1 What is the most likely diagnosis?

Short answer

Given the history of travel in an area endemic for Lyme disease and the history of asymptomatic expanding annular lesions, the most likely diagnosis is multiple lesions of erythema migrans associated with Lyme disease.

Long answer

The figure shows large macular non-scaly patches on the anterior and posterior thighs, with central clearing and an advancing erythematous edge. The history of travel in an area that is endemic for Lyme disease (Limousin, France) and the gradually expanding plaques should alert doctors to the possibility of a diagnosis of erythema migrans in Lyme disease.

Lyme disease is the most common tick borne disease in Europe and North America,1 and it is caused by transmission of the spirochaetes of …

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