Medical Definition of Erythema chronicum migrans
Erythema chronicum migrans: The classic initial rash of Lyme disease. In the early phase of the illness, within hours to weeks of the tick bite, the local skin develops an expanding ring of unraised redness. There may be an outer ring of brighter redness and a central area of clearing. For more information, see Lyme Disease.
Last Editorial Review: 8/28/2013
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