Lyme Disease

Key Features

Essentials of Diagnosis

• Characteristic skin lesion (erythema migrans) 3–30 days after tick bite

• Arthritis, usually pauciarticular, occurring about 4 weeks after appearance of skin lesion

• Headache, chills, and fever

• Residence or travel in an endemic area during the late spring to early fall

General Considerations

• Caused by Borrelia burgdorferi

• Transmitted by an infected deer tick (Ixodes species)

• Most cases with rash are recognized in spring and summer, when most tick bites occur

• However, because the incubation period for joint and neurologic disease may be months, cases may present at any time

Demographics

• The most prominent endemic areas in the United States include the Northeast, upper Midwest, and West Coast

• Northern European countries also have high rates of infection

Clinical Findings

Symptoms and Signs

• Erythema chronicum migrans

  • Most characteristic feature of Lyme disease

  • Recognized in 60–80% of patient

  • Ring of erythema develops at the site and spreads over days

  • May attain a diameter of 20 cm

  • Center of the lesion may clear (resembling tinea corporis), remain red, or become raised

  • Mild tenderness may occur

  • Untreated, the rash lasts days to 3 weeks

• Most patients are otherwise asymptomatic

• Some have fever (usually low-grade), headache, and myalgias

• Multiple satellite skin lesions, urticaria, or diffuse erythema may occur

• Arthritis

  • Develops several weeks to months after the bite in up to 50% of patients

  • Recurrent attacks of migratory, monoarticular, or pauciarticular arthritis involving the knees and other large joints occur

  • Each attack lasts for days to a few weeks

  • Fever is common and may be high

  • Complete resolution between attacks is typical

  • Chronic arthritis develops in < 10% of patients, more often in those with the DR4 haplotype

• Neurologic manifestations

  • Develop in up to 20% of untreated patients

  • Usually consist of Bell palsy, aseptic meningitis, or polyradiculitis

  • Peripheral neuritis, Guillain-Barré syndrome, encephalitis, ataxia, chorea, and other cranial neuropathies are less common

  • Usually self-limited if left untreated but may be chronic or permanent

Differential Diagnosis

• Rash may resemble pityriasis, erythema multiforme, a drug eruption, or erythema nodosum

• Arthritis may resemble juvenile rheumatoid arthritis, reactive arthritis, septic arthritis, reactive effusion from a contiguous osteomyelitis, rheumatic fever, leukemic arthritis, systemic lupus erythematosus, and Henoch-Schönlein purpura

Diagnosis

• Clinical; serologic testing may support the clinical diagnosis

• Serologic diagnosis of Lyme disease is based on a two-test approach: an ELISA and an immunoblot to confirm a positive or indeterminate ELISA

• Antibodies may not be detectable until several weeks after infection has occurred; therefore, serologic testing in children with a typical rash is not recommended

• Children with arthritis

  • May have moderately elevated ESRs and WBC counts

  • Antinuclear antibodies and rheumatoid factor tests are negative or nonspecific

  • Streptococcal antibodies are not elevated

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