Synopsis
Recognise erythema migrans and disseminated Lyme borreliosis, use clinical diagnosis and two-tier serology at the right time, and select manifestation-specific treatment and escalation.
- Lyme borreliosis is caused by Borrelia burgdorferi sensu lato transmitted by infected Ixodes ticks; risk rises with attachment duration but a recalled bite is not required.
- Erythema migrans is an expanding erythematous lesion, usually appearing one to four weeks after a bite; it is not usually hot, painful or itchy and may lack textbook central clearing.
- Diagnose erythema migrans clinically and treat without laboratory testing because early serology can be negative.
- Without erythema migrans, first-line testing is a validated Lyme antibody ELISA followed by immunoblot when the ELISA is positive or equivocal.
- If an ELISA is negative within four weeks of symptom onset but suspicion remains, repeat it four to six weeks after the first sample.
- Early disseminated disease includes multiple erythema migrans lesions, cranial neuropathy, painful radiculopathy, lymphocytic meningitis and carditis.
- Late manifestations include intermittent large-joint arthritis, acrodermatitis chronica atrophicans and uncommon neurological syndromes; antibodies can remain positive after cure.
- First-line adult treatment for erythema migrans or non-focal symptoms is doxycycline 100 mg twice daily or 200 mg once daily for 21 days.
- Unstable Lyme carditis requires monitored admission and ceftriaxone 2 g intravenously once daily for 21 days, switching to oral doxycycline when clinically appropriate.
- Do not give routine antibiotic prophylaxis to an asymptomatic person after a tick bite in the UK; remove the tick promptly and explain symptoms that require review.
Key red flags
Syncope, presyncope, chest pain, dyspnoea or palpitations with PR prolongation or atrioventricular block may be Lyme carditis and can deteriorate rapidly.
Facial palsy with meningism, radicular pain, objective weakness, bladder dysfunction, encephalopathy or focal deficit requires an urgent neurological pathway.
A hot swollen joint still requires septic-arthritis assessment; Lyme arthritis cannot be assumed from exposure or a positive antibody result alone.
Pregnancy does not justify delayed treatment; choose a pregnancy-compatible regimen with obstetric and infection advice when disease is disseminated.
Immunocompromise, diagnostic uncertainty or progression despite an appropriate first course warrants specialist review and reconsideration of alternatives.
Erythema migrans is a clinical diagnosis and should be treated promptly even when serology is negative or has not been sent.
Facial palsy, painful radiculoneuritis, sensory symptoms or lymphocytic meningitis can appear weeks after infection and require objective localisation.
Fluctuating atrioventricular block causes dizziness, syncope, palpitations, chest discomfort or breathlessness; myocarditis and ventricular dysfunction are less common.
Investigation priorities
Recognise the manifestation that does not require laboratory confirmation.
Screen a symptomatic person without erythema migrans when Lyme disease is clinically plausible.
Management branches
A typical expanding lesion follows plausible tick exposure, with or without constitutional symptoms.
- Document lesion size, appearance, onset and exposure; distinguish it from a small immediate hypersensitivity reaction that appears and resolves quickly after a bite.
- Do not request serology routinely because antibodies may be absent and the result does not alter treatment of a typical lesion.
- Give first-line doxycycline 100 mg orally twice daily or 200 mg once daily for 21 days when suitable.
- Use amoxicillin 1 g orally three times daily for 21 days when doxycycline is unsuitable; azithromycin 500 mg daily for 17 days is a second alternative after interaction and cardiac review.