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The first symptom is a rash called erythema migrans (EM), which is usually a flat, reddish rash that spreads from the site of the tick bite. The rash usually is larger than 2 inches wide and can grow larger. It often develops a central clear area known as a bull's eye. The rash usually doesn't itch or hurt. Other symptoms at this stage can include fever, muscle and joint aches, fatigue, headache and a severe stiff neck. In some cases, there are two or more of these well-defined rashes.

Over several days to weeks after the tick bite, Lyme disease can cause neurological problems, including meningitis, which is an infection of the lining of the brain and spinal cord; and Bell's palsy, a weakness in facial muscles caused by nerve injury. Lyme disease also can cause carditis, an inflammation of the heart muscle that can cause irregular heart rhythms with fainting or dizziness. Months to years after Lyme disease affects the heart, changes can be seen on an electrocardiogram (EKG) even when there are no symptoms. Lyme disease also can cause either a chronic arthritis that commonly affects one knee or episodes of swelling in several joints, called migratory arthritis.

In later stages of Lyme disease, patients can experience problems with memory and concentration.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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