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For further information, see CMDT Part 34-11: Lyme Disease (Lyme Borreliosis)

Key Features

Essentials of Diagnosis

  • Erythema migrans, a flat or slightly raised red lesion that expands with central clearing

  • Headache or stiff neck

  • Arthralgias, arthritis, and myalgias; arthritis is often chronic and recurrent

  • Wide geographic distribution, with most cases in the northeast, mid-Atlantic, upper midwest, and Pacific coastal regions of the United States

General Considerations

  • Causative spirochete varies by geography

    • In the United States, it is Borrelia burgdorferi senu strictu

    • In Europe and Asia, it is Borrelia garinii and Borrelia afzelli

  • Incidence of disease is significantly higher when tick attachment is for longer than 72 h

  • The percentage of ticks infected varies on a regional basis. In the northeast and midwest, 15–65%, in the west, only 5%

  • Congenital infection has been documented

  • Ixodes scapularis is capable of transmitting other infections in addition to Lyme disease, including babesiosis and human granulocytic anaplasmosis (formerly human granulocytic ehrlichiosis)

    • Coinfection with two or even all three of these organisms can occur, causing a clinical picture that is not "classic" for any of these diseases

    • Coinfection should be considered and excluded in patients who have

      • Persistent high fevers 48 hours after starting appropriate therapy for Lyme disease

      • Persistent symptoms despite resolution of rash

      • Anemia, leukopenia, or thrombocytopenia


  • Most cases are reported from the mid-Atlantic, northeastern, and north central regions of the country

  • True incidence is unknown and overreporting continues to be a problem for following reasons:

    • Serologic tests are not standardized

    • Clinical manifestations are nonspecific

    • Serology tests are insensitive in early disease

  • Most infections occur in the spring and summer

Clinical Findings

Symptoms and Signs

  • Stage 1, early localized infection

    • Erythema migrans

      • A flat or slightly raised red lesion at the bite site ~1 week after the tick bite (range, 3–30 days; median, 7–10 days)

      • Common in areas of tight clothing such as the groin, thigh, or axilla

      • The lesion expands over several days

      • Classic lesion progresses with central clearing ("bulls-eye" lesion); often there is a more homogeneous appearance or even central intensification

    • Concomitant viral-like illness develops in most patients and is characterized by

      • Myalgias, arthralgias

      • Headache, fatigue

      • Fever may or may not be present

  • Stage 2, early disseminated infection (weeks to months later)

    • Bacteremia (in up to 50–60% of patients with erythema migrans)

    • Secondary skin lesions

      • Develop within days to weeks of original infection in about 50% of patients

      • Lesions similar to primary lesion but smaller

      • A cutaneous hypopigmented skin lesion called a borrelial lymphocytoma develops rarely

    • Malaise, fatigue, fever, headache, neck pain generalized achiness common with skin lesions

    • Myopericarditis, with atrial or ventricular arrhythmias and heart block (4–10%)

    • Neurologic manifestations (10–15%)

      • Aseptic meningitis with mild headache and neck stiffness

      • Cranial nerve VII neuropathy (eg, facial palsy)


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