Infectious Disease

Lyme disease

Lyme disease is a multisystem infection caused by Borrelia species and transmitted by Ixodes ticks; diagnose erythema migrans clinically, use accredited serology for presentations without the rash, and escalate focal neurological, cardiac, ocular, joint, pregnancy and paediatric disease through the current NICE pathway.

In a nutshell

Lyme disease is a Borrelia infection transmitted by Ixodes ticks. Diagnose erythema migrans clinically and treat without waiting for serology; without the rash, use UKAS-accredited two-tier ELISA and immunoblot testing with repeat testing when early. Recognise facial palsy, meningitis, uveitis or keratitis, myocarditis or heart block, and large-joint arthritis as focal disease requiring specialist or emergency care. Use syndrome-specific NICE antibiotics, manage pregnancy and children with appropriate specialist advice, and do not continue indefinite antibiotics for persistent non-specific symptoms.

Classic presentation

A walker develops an expanding red rash after outdoor exposure, or later presents with facial palsy, syncope from heart block or a swollen large joint without recalling a tick bite.

Key points

Erythema migrans is an expanding rash, often 1–4 weeks after exposure, and is treated clinically without waiting for serology.
Without erythema migrans, use a validated IgM/IgG ELISA followed by immunoblot if positive or equivocal; early negatives may need repeat testing.
Lyme disease can cause facial palsy, meningitis or radiculopathy, myocarditis with heart block, uveitis or keratitis, and large-joint arthritis.
Use current NICE syndrome-specific antibiotic regimens; check BNF and specialist pathways for children, pregnancy and focal disease.
Syncope, palpitations, breathlessness, chest symptoms, meningitis or visual change require emergency assessment.
After two completed courses, do not routinely give more antibiotics for ongoing non-specific symptoms; reassess for alternatives, reinfection and organ damage.

First-line investigation

Clinical diagnosis for erythema migrans; otherwise validated two-tier ELISA and immunoblot testing with specialist-led organ investigations for focal disease.

Management

Identify emergencies

Arrange emergency assessment for syncope, breathlessness, palpitations, chest symptoms, suspected heart block, meningitis, encephalitis, severe neurological deficit, uveitis or keratitis.^1,5
Discuss focal disease urgently with the appropriate infection, neurology, cardiology, rheumatology or ophthalmology team without delaying indicated treatment.^1,7

Diagnose in the correct order

Treat a typical expanding erythema migrans rash clinically; if there is no rash, use a UKAS-accredited two-tier ELISA and immunoblot pathway and interpret results with exposure and symptoms.^1,6,4
Repeat an early negative ELISA after 4–6 weeks if suspicion persists, and review alternative diagnoses and laboratory quality rather than relying on unvalidated private tests.^1,6,4

Start syndrome-specific antibiotics

For adults and young people aged 12 and over with erythema migrans, use the current NICE oral doxycycline or amoxicillin regimen and check BNF for prescribing details, contraindications and pregnancy.^1,7
Use the focal-disease regimen and duration for neuroborreliosis, arthritis, acrodermatitis or carditis; involve specialists for children, pregnancy and central nervous system or unstable cardiac disease.^1,5,7

Monitor heart and organ complications

Obtain an ECG and admit for monitoring when Lyme carditis or significant conduction disease is suspected; unstable disease needs urgent cardiology and intravenous specialist-led therapy.^1,5,7
Use emergency CNS and ophthalmology pathways for meningitis, encephalitis, uveitis or keratitis, and do not delay time-critical treatment for Lyme test results.^1,5

Reassess rather than over-treat

Explain the possible Jarisch–Herxheimer reaction, review symptoms that fail to improve or recur, and after two completed courses avoid routine further antibiotics while assessing alternatives, reinfection and organ damage.^1,2,4
Prevent future bites with protective clothing, repellent, skin checks and prompt correct tick removal; routine UK post-exposure antibiotic prophylaxis is not recommended.^1,3,2

Exam traps

Do not wait for serology when the rash is typical erythema migrans.
A tick bite may not be recalled and a rash is not always a classic bullseye, so ask about outdoor exposure and look at the whole clinical picture.
A negative early ELISA does not exclude Lyme disease; repeat it 4–6 weeks later if suspicion remains.
Young people under 18 with focal disease need specialist discussion; do not treat complicated paediatric disease as simple erythema migrans.
Consider Lyme carditis in unexplained heart block or syncope; do not use azithromycin with cardiac abnormalities.
Persistent fatigue or pain after treatment does not prove active infection and is not an indication for indefinite antibiotics.

Illustrations

Erythema migrans (bull's-eye rash)A clinical photograph of the expanding erythema migrans rash with central clearing at a tick-bite site, the hallmark of early Lyme disease.James Gathany / CDC, Wikimedia Commons · Public domain

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.