What is the most appropriate next step in managing a patient with a rash, fatigue, headaches, and mild chills after a recent hike in a wooded area, suspected to have early localized or early disseminated Lyme disease?

Management of Early Localized Lyme Disease

Empirically prescribe doxycycline 100 mg twice daily for 10 days without serologic testing (Option D). 1, 2

Clinical Diagnosis is Sufficient

• This patient presents with classic erythema migrans (EM): a large (20 cm) expanding rash with faint central clearing following woodland exposure in an endemic area, making Lyme disease the clear diagnosis 2, 3
• Erythema migrans is a clinical diagnosis that does not require laboratory confirmation for treatment 2
• The IDSA explicitly states that patients with EM can be reasonably diagnosed and treated based on history and clinical signs alone 4, 2

Why Serologic Testing is Not Indicated

• Two-tier serology is insensitive in early localized Lyme disease because antibodies have not yet developed at this stage 2
• Antibodies typically develop approximately 2 weeks after symptom onset, and this patient is only 10 days post-exposure with 3-4 days of symptoms 4
• Initial testing will likely be negative and would only delay appropriate treatment 2
• Starting antibiotics immediately prevents dissemination to joints, heart, and nervous system 2

Recommended Treatment Regimen

• Doxycycline 100 mg orally twice daily for 10 days is the first-line treatment for early localized Lyme disease 1
• The IDSA guidelines specifically state that 10 days of therapy is sufficient when doxycycline is used 1
• Doxycycline has the added advantage of treating human granulocytic anaplasmosis (HGA), which may occur as a coinfection from the same tick bite 1

Why Other Options are Incorrect

• Option A is wrong: Ordering antibody testing now would be falsely negative due to insufficient time for antibody development, and waiting for results delays necessary treatment 4, 2
• Option B is wrong: Lumbar puncture is only indicated for neurologic manifestations (meningitis, cranial nerve palsies beyond isolated facial palsy, radiculopathy), which this patient does not have 1
• Option C is wrong: Trimethoprim-sulfamethoxazole is completely ineffective against Borrelia burgdorferi and should never be used for Lyme disease 1

Alternative Regimens (if doxycycline contraindicated)

• Amoxicillin 500 mg three times daily for 14-21 days 1, 2
• Cefuroxime axetil 500 mg twice daily for 14-21 days 1, 2
• First-generation cephalosporins (like cephalexin), fluoroquinolones, and macrolides are not recommended 1, 2

Critical Monitoring Points

• Clinical improvement should occur within days to weeks of starting antibiotics 2
• The EM lesion may take several weeks to completely resolve even with appropriate treatment 2
• High fever persisting >48 hours despite appropriate therapy should raise suspicion for coinfection with Anaplasma or Babesia 2
• Unexplained leukopenia, thrombocytopenia, or anemia also suggest possible coinfection 2

Common Pitfalls to Avoid

• Do not delay treatment while waiting for serologic confirmation in patients with characteristic EM 2
• Do not use first-generation cephalosporins, which are inactive against B. burgdorferi 1
• Advise patients to avoid excessive sunlight while on doxycycline due to photosensitivity risk 5
• Instruct patients to take doxycycline with 8 ounces of fluid to reduce esophageal irritation risk 1, 5