Lesson
Turn a Tick Bite Into a Measured Decision
Most tick bites do not become Lyme disease. Vector identity, endemicity, engorgement, attachment duration, and time since removal determine whether observation or prophylaxis is appropriate.
- Ixodes
- Endemicity
- Attachment
- Engorgement
- Prophylaxis
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Start with the vector and place
In the United States, blacklegged Ixodes ticks transmit the Borrelia species that cause Lyme disease. Risk varies across and within states, so use current local public health data rather than a national stereotype.
Remove first and assess second
Use fine tipped tweezers close to the skin and pull upward with steady pressure. Do not burn, twist, crush, smother, or delay removal while seeking perfect identification.
Reserve prophylaxis for high risk bites
A high risk decision integrates an Ixodes tick, exposure in a highly endemic area, engorgement or attachment of at least 36 hours, treatment within 72 hours of removal, and doxycycline safety.
Calculate the single dose
Eligible adults receive doxycycline 200 mg once. Children of any age receive 4.4 mg/kg once to a maximum of 200 mg. Prophylaxis does not prevent every Ixodes transmitted infection.
Quick check
Lesson
Recognize the Rash Without Requiring a Bullseye
Erythema migrans is an expanding lesion with variable color and shape. Multiple lesions or neurologic and cardiac symptoms indicate dissemination beyond the original skin site.
- Expansion
- Variable morphology
- Mimics
- Dissemination
- Objective arthritis
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Look for expansion, not one perfect shape
Erythema migrans often expands over days and commonly exceeds 5 cm. It may be uniformly red, target shaped, vesicular, crusted, or faint, and it does not require central clearing.
Distinguish common mimics
A local bite reaction is usually smaller and appears soon after the bite. Tinea often has scale. Cellulitis is often tender and warm. Drug eruptions, erythema multiforme, and STARI require exposure and morphology context.
Screen for early dissemination
Multiple lesions, facial palsy, meningitis, radicular pain, palpitations, syncope, dyspnea, or chest pain move the case beyond uncomplicated localized disease.
Define late objective disease
Lyme arthritis produces obvious swelling of one or a few large joints, often the knee. Arthralgia without objective synovitis is not the same manifestation.
Quick check
Lesson
Use Serology for the Question It Can Answer
Typical erythema migrans is a clinical diagnosis. Other compatible manifestations use FDA cleared standard or modified two tier serology interpreted through illness duration and pretest probability.
- Clinical diagnosis
- Two tier testing
- Window period
- IgM boundary
- No test of cure
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Treat typical erythema migrans clinically
Acute serology can be falsely negative when the rash appears. In a credible exposure setting, a typical lesion should receive prompt treatment without requiring laboratory confirmation.
Use the complete two tier algorithm
Standard two tier testing uses an EIA followed by immunoblot when indicated. Modified two tier testing uses a second FDA cleared EIA. A stand alone immunoblot or unvalidated specialty assay is not equivalent.
Respect the antibody window
Serologic tests can be falsely negative during the first 4 to 6 weeks. When an atypical early lesion remains suspicious, acute and convalescent testing can clarify the trajectory.
Do not use antibody as microbial burden
IgM should not drive diagnosis after more than 30 days of illness. IgG can remain positive for years after treatment, so repeat titers do not prove cure, failure, or reinfection.
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Lesson
Match the Oral Regimen to the Patient and Stage
Doxycycline, amoxicillin, and cefuroxime are effective for uncomplicated erythema migrans. Regimen choice must preserve exact dose, duration, administration, and patient fit.
- Doxycycline
- Amoxicillin
- Cefuroxime
- Pediatric calculation
- Administration
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Use the adult regimens precisely
Adults can receive doxycycline 100 mg twice daily for 10 days, amoxicillin 500 mg three times daily for 14 days, or cefuroxime 500 mg twice daily for 14 days. Azithromycin is less effective and reserved for patients unable to use the preferred agents.
Calculate pediatric exposure
Children can receive doxycycline 4.4 mg/kg/day divided twice daily, amoxicillin 50 mg/kg/day divided three times daily, or cefuroxime 30 mg/kg/day divided twice daily, each within its maximum dose.
Protect doxycycline delivery
Separate polyvalent cations and interacting tube feeds. Use adequate water and upright posture to reduce esophageal injury, and counsel about photosensitivity.
Interpret early worsening carefully
A mild transient inflammatory worsening can occur during the first 24 hours. Severe hypotension, respiratory compromise, mucosal disease, persistent deterioration, or later symptoms require evaluation for allergy, sepsis, or another cause.
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Lesson
Separate Peripheral and Meningeal Disease From Brain or Cord Injury
Facial palsy, radiculoneuritis, and meningitis are common neurologic patterns. Objective parenchymal brain or spinal cord disease is uncommon and changes the route of therapy.
- Facial palsy
- Corneal protection
- Radiculoneuritis
- Meningitis
- Parenchymal CNS
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Protect the eye in facial palsy
Lyme facial palsy can affect one or both sides. When eyelid closure is impaired, lubrication, patching, or taping protects the cornea while antibiotics treat infection.
Recognize radiculoneuritis and meningitis
Severe shooting limb or truncal pain, weakness, headache, photophobia, fever, and neck stiffness should trigger focused neurologic and meningitis evaluation.
Choose route from the patient
Meningitis, cranial neuropathy, or radiculoneuritis without parenchymal CNS disease can use oral doxycycline or IV ceftriaxone, cefotaxime, or penicillin G for 14 to 21 days. Oral and IV routes can be changed as the patient stabilizes.
Escalate parenchymal disease
Objective encephalitis, myelitis, or other brain or spinal cord parenchymal involvement receives specialist directed IV therapy and a broad neurologic differential.
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Lesson
Treat Conduction Risk as a Reversible Emergency
Lyme carditis can progress rapidly through atrioventricular block. Symptoms, PR duration, block degree, rhythm, and myocardial findings determine outpatient or monitored care.
- Symptom screen
- PR interval
- Telemetry
- Ceftriaxone
- Temporary pacing
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Screen for cardiac involvement
Palpitations, lightheadedness, syncope, dyspnea, chest pain, edema, or exercise intolerance warrant ECG and cardiac evaluation. Routine ECG is not required in every asymptomatic patient.
Treat mild disease orally
First degree block with PR below 300 milliseconds and no severe features can use doxycycline, amoxicillin, or cefuroxime for 14 to 21 days with close follow-up.
Hospitalize severe carditis
Symptoms, PR at least 300 milliseconds, second or third degree block, another significant arrhythmia, or myopericarditis requires continuous monitoring and initial IV ceftriaxone. Treatment should not wait for serology.
Use reversible pacing logic
Temporary pacing is preferred when symptomatic bradycardia requires pacing. After high grade block and symptoms resolve, transition to an effective oral agent can complete a total 14 to 21 day course.
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Lesson
Treat the Joint, Then Recognize When Infection Is No Longer the Driver
Lyme arthritis produces objective swelling, usually in a large joint. Initial antimicrobial care, response guided retreatment, and postantibiotic inflammatory care are distinct phases.
- Objective synovitis
- Twenty eight days
- Response grade
- IV ceftriaxone
- Postantibiotic arthritis
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Define objective disease
Obvious swelling of one or a few large joints, often a knee, is the core manifestation. Serum two tier serology is highly sensitive at this stage.
Protect against septic arthritis
Fever, severe pain, inability to bear weight, critical illness, immunocompromise, or another high risk feature can require urgent arthrocentesis with cell count, Gram stain, culture, and crystals.
Treat and grade response
Initial Lyme arthritis receives 28 days of oral doxycycline, amoxicillin, or cefuroxime. Partial improvement can be observed or receive a second oral course. Minimal response can receive IV ceftriaxone for 14 to 28 days after reassessment.
Stop antibiotics after adequate oral and IV care
Persistent synovitis after an adequate oral course and an adequate IV course is managed as postantibiotic inflammatory arthritis with rheumatology, not repeated antimicrobial cycles.
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Lesson
Individualize Exposure Without Sacrificing Effective Care
Age, pregnancy, lactation, allergy, dosage form, and adherence change regimen selection. They do not justify leaving objective Lyme disease untreated.
- Children
- Pregnancy
- Lactation
- Allergy
- Formulation
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Use current pediatric reasoning
Doxycycline can be used in children when the manifestation and regimen support it. Amoxicillin and cefuroxime remain effective alternatives for many uncomplicated presentations.
Use narrative pregnancy and lactation reasoning
Amoxicillin or cefuroxime is often preferred for uncomplicated early disease when effective and tolerated. Doxycycline decisions are individualized from manifestation, duration, allergy, maternal risk, and alternatives.
Clarify allergy before narrowing care
Separate intolerance, delayed rash, immediate hypersensitivity, and severe cutaneous reactions. The phenotype determines whether another beta lactam, doxycycline, challenge, desensitization, or specialist input is appropriate.
Make the regimen executable
Confirm suspension concentration, tablet swallowing, dosing frequency, cation separation, sun exposure, school or work schedule, cost, and the person responsible for follow-up.
Quick check
Lesson
Keep New Evidence From Becoming More Unnecessary Antibiotics
Persistent fever, cytopenias, or hemolysis can signal coinfection. Persistent nonspecific symptoms after adequate treatment require validation and a broad care plan, not unsupported antimicrobial extension.
- Anaplasma
- Babesia
- Reinfection
- Post treatment symptoms
- Shared goals
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Look for coinfection
High fever, leukopenia, thrombocytopenia, transaminitis, hemolytic anemia, jaundice, or persistent fever should trigger evaluation for Anaplasma, Babesia, and other locally relevant pathogens. Doxycycline does not treat Babesia.
Recognize reinfection
Prior disease and persistent antibody do not create reliable immunity. A new exposure with a new expanding lesion or another new objective manifestation can represent reinfection.
Evaluate prolonged symptoms broadly
Fatigue, pain, cognitive difficulty, sleep disturbance, and exercise intolerance deserve a structured evaluation for medication, endocrine, mood, sleep, infectious, inflammatory, and other causes.
Do not use unsupported prolonged antibiotics
Without objective evidence of reinfection or treatment failure, additional antibiotics do not improve prolonged nonspecific symptoms and can cause catheter infection, allergy, diarrhea, and other serious harm. Care should remain compassionate and functional.
Quick check
Lesson
Use Stage, Anatomy, and Physiology to Choose the Next Move
Lyme care becomes reliable when each decision begins with the manifestation, threat level, test window, prior therapy, and exact exposure rather than one positive result or one remembered bite.
- Stage
- Anatomy
- Severity
- Testing
- Ownership
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Connect exposure, stage, testing, treatment, and follow-up without losing the patient context.
Lead with the manifestation
An expanding rash, facial palsy, meningitis, carditis, and objective arthritis have different testing and treatment pathways even when the organism is the same.
Let physiology determine setting
Syncope, high grade block, encephalomyelitis, sepsis physiology, or threatened joint safety requires urgent monitored or procedural care.
Use tests to reduce uncertainty
Testing should answer a defined question. Typical erythema migrans is clinical, later objective disease uses two tier serology, and selected CSF or synovial testing supports rather than replaces the clinical pathway.
Close the loop
Document dose, duration, administration, red flags, follow-up date, who reviews pending results, and what finding triggers escalation or a different diagnosis.
Quick check
Module test
Check the connections.
Each attempt draws 10 questions from the complete 156 question bank.
Each attempt draws a fresh set and rearranges the answer choices.
References
Current clinical foundation.
Lecture material was synthesized with the following contemporary guidance. Verify local policy and current guidance before applying clinical information.