Lyme disease, named after a town in Connecticut, is caused by a spirochete, Borrelia burgdorferi, that is transmitted by the bite of the Ixodes tick of North America and Europe.
The characteristic skin eruption, erythema chronicum migrans, develops at the site of the bite after an incubation period of up to 30 days.
An expanding, often raised, crimson rim surrounds a more purple red central lesion. There may be associated scaling. Burning or itching is common, but the lesion may be asymptomatic.
More than half of the patients develop systemic symptoms including arthritis, meningitis, neuritis, and myocarditis.
- Early disease responds well to amoxicillin 1 gram po tid or doxycycline 100 mg po tid for three weeks.
- Evidence of more than minimal systemic disease necessitates the use of IV ceftriaxone or benzylpenicillin, again for three weeks.