Saturday, June 29, 2013

Erythema Migrans: Classic Lyme

Presented by Yoon Cohen, D.O. and David Elpern, M.D.

Abstract:  38-year-old man with history of tick bite and expanding annular lesion

HPI: The patient is a 38-year-old man with a 4-day history of and expanding red annular patch on the right inner thigh. He had a tick bite in this area ~ 10 days prior. He has not been treated with any antibiotics at this time and has had denied no flu-like or other associated constitutional symptoms.  He lives in an endemic area and has had many tick bites in the past.

O/E: The skin examination showed a healthy and pleasant man with a well-defined 15 cm pink to red annular patch with a central pink oval shaped patch on his right thigh.  It has a "bull's eye" appearance.  There are no other cutaneous findings.

Clinical Photo:

Diagnosis: Erythema Migrans (Early Lyme Disease)


Lyme disease is caused by the spirochete Borrelia burgdorferi. Erythema migrans is the most common clinical manifestation of Lyme disease. It typically develops 7-14 days after tick detachment and is characterized by a rapidly expanding, erythematous annular patch or plaque. 

The diagnosis of erythema migrans is based on the clinical presentation and history of recent exposure in the endemic regions. Although the skin lesion cannot be considered pathognomonic of Lyme disease, erythema migrans is so distinctive that serologic testing for antibodies against B.burgdorferi is generally unnecessary. These serologic tests have high false negative results in as many as 60% of cases.

Treatment for Lyme disease depends on the stage. If there is only a tick bite, single dosage of doxycycline 200 mg is considered adequate if administered within 2 - 3 days.  However, if a patient presents with erythema migrans, doxycycline 100 mg twice daily for 14 days (range, 10 to 21 days) is currently advised.  (Amoxicillin is an alternate treatment).  For secondary and tertiary Lyme disease the treatment can be more complex.

The references below give much more detailed information.  Post-Lyme Disease syndrome is controversial and has generated a lot of ink.  See Michael Spector's fine New Yorker piece referenced below.

Early Lyme Disease
Gary P. Wormser, M.D.
N Engl J Med 2006; 354:2794-2801
(This is an extremely helpful article.  Although it is seven years old, little has changed re garding hte literature on chronic Lyme disease.  If you can't get access to the full text of this article, we will send you a pdf.)

2.  Annals of Medicine
The Lyme-disease infection rate is growing. So is the battle over how to treat it.
by Michael Specter The New Yorker July 1, 2013
This is in the current New Yorker as we prepare this post.  It is a level-headed review of Lyme disease from a top science writer.  This article will help the public as well as physicians. 

3.  Patient Friendly Material

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