The Rational Clinical Examination
David L. Simel, Drummond Rennie
Erythema Migrans
Carrie D. Tibbles, Jonathan A. Edlow
Clinical Scenario
Topics Discussed:
borrelia burgdorferi, erythema migrans, lyme disease, tick bite, ticks
Excerpt:
"A 22-year old man presents to the emergency department with a
red rash on his left shoulder. The rash is slightly itchy and has
increased in size since he first noticed it, 3 days ago. It is July,
and he has been working outdoors in New Jersey, but does not recall
a tick bite. He is afebrile. The rash is a flat oval homogeneous
erythema, 14 cm along its long axis, without central clearing (Figure 61-2).
Other than a small minimally tender 1.5 x 1.5-cm
lymph node in the left axilla, his physical examination is normal.
You think that erythema migrans is a strong possibility and consider
treating him without any further testing.In 1908, the Swedish dermatologist Afezelius1 described
erythema migrans as an expanding erythema with central clearing
that occurred at the site of a bite of the European sheep tick Ixodes ricinus. Over the ensuing decades,
European investigators documented the details of the rash (previously referred
to as erythema chronicum migrans), its association with tick bites,
its responsiveness to antibiotics, and its association with other
manifestations of what is now known as Lyme disease or Lyme borreliosis.1 The
term Lyme arthritis was coined in the
late 1970s after an investigation of a statistically improbable
cluster of what had been erroneously diagnosed as juvenile rheumatoid
arthritis in the Lyme, Conn, area. This investigation, headed by
a team from Yale University, focused on the arthritis, but it soon
became clear that cardiac, neurological, skin, and other manifestations
were part of a systemic disease transmitted by the bite of an Ixodes scapularis tick.2–4 In
1982, Burgdorfer5 and colleagues at the National
Institutes of Health Rocky Mountain Laboratory discovered the causative
agent, a novel bacterium, Borrelia burgdorferi (sensu
stricto). Shortly thereafter, 2 closely related spirochetes, Borrelia afzelii and Borrelia garinii, were isolated from
European cases of erythema migrans.6,7 Collectively,
these 3 bacteria are termed B burgdorferi,
sensu lato. For years, erythema migrans was considered to be pathognomonic
of Lyme disease. However, recent reports of erythema migrans–like
rashes in nonendemic areas of the United States have called that
concept into question...."
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