Lyme disease, erythema chronicum migrans
Erythema chronicum migrans is the initial lesion of Lyme disease, and often appears at the site of the infecting tick bite. It is a red, enlarging rash, flat or slightly raised, and may reach from 4 to 20 inches across (the average rash is 6 inches). (Image courtesy of the Centers for Disease Control and Prevention.)
Update Date: 5/19/2008 Updated by: Jatin M. Vyas, MD, PhD, Instructor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Massachusetts General Hospital. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.