Erythema migrans

Skin biopsy obtained from within 1 cm of the peripheral margin of an erythema migrans lesion showing endothelial cell injury with incipient fibrin deposition and regenerative alterations of the endothelium. There is luminal attenuation and a very sparse infiltrate. Similar changes are noted in the central nervous system, synovium, and myocardium in advanced Lyme disease.