A nine-year-old girl, Skye, comes to see you with her parents. She has a two-day history of a red, circular and enlarging rash on her right calf, which they describe as looking like a ‘bull’s eye’. She has also been feeling generally unwell with headaches, muscle aches, fatigue and fever. They tell you in passing that they returned from a holiday in Scotland a week ago.
Since reporting began in 1986, Public Health England reports that the number of laboratory-confirmed Lyme disease cases in the UK has steadily risen. The National Institute for Health and Care Excellence has recently published guidance designed to create a consistent approach to diagnosing and managing patients with suspected or confirmed Lyme disease. In addition, this guidance aims to raise awareness of Lyme disease amongst healthcare professionals, so it is considered a possible differential diagnosis where appropriate.
What is Lyme disease?
Lyme disease is a bacterial infection caused by Borrelia burgdorferi. It is transmitted to humans through a bite from an infected Ixodes tick; these ticks are usually found in wooded and grassy areas (both urban and rural) between April and October. Lyme disease is most common in parts of the USA, Canada, Europe, and Asia. In the UK, there are approximately 1000 serologically confirmed cases annually, with the majority occurring in the South of England and the Scottish Highlands.
What are the symptoms of Lyme disease?
The most characteristic feature of Lyme disease is erythema migrans:
- A red, circular rash, with central clearing and a ‘bulls eye’
- Usually at the site of the tick bite, developing three days to three months after the bite.
- Enlarging, but usually not painful or itchy
Lyme disease can also cause non-specific symptoms, including fever, sweats, malaise, lymphadenopathy, neck pain or stiffness, fatigue, myalgia, arthralgia, headaches, paraesthesia or cognitive impairment (e.g. difficulties with memory and concentration).
Lyme disease can also present with a range of focal symptoms, including:
- Neurological symptoms (e.g. unexplained cranial nerve palsies, meningitis or unexplained radiculopathy)
- Inflammatory arthritis
- Cardiac problems (e.g. heart block or pericarditis)
- Eye symptoms (e.g. uveitis or keratitis)
- Skin rashes (e.g. acrodermatitis chronica atrophicans or lymphocytoma)
How do I diagnose Lyme disease?
Patients with erythema migrans should be diagnosed and treated for Lyme disease; lab testing is not required in these cases.
Patients without erythema migrans:
- Where Lyme disease is suspected, offer an ELISA for Lyme disease and if the suspicion is high, consider starting antibiotic treatment whilst awaiting the results.
- Positive or equivocal ELISA:
- Conduct an immunoblot test for Lyme disease.
- Negative ELISA:
- Where a clinical suspicion of Lyme disease remains, in patients who had an ELISA within four weeks of the onset of their symptoms repeat the ELISA 4 to 6 weeks later.
- Where a clinical suspicion of Lyme disease remains, in patients who have had symptoms for at least 12 weeks, conduct an immunoblot.
- Lyme disease should be diagnosed in those who have a positive immunoblot and Lyme disease symptoms.
- Positive or equivocal ELISA:
In patients younger than 18, the diagnosis and management of Lyme disease should be discussed with a specialist, except for uncomplicated erythema migrans.
How do I treat Lyme disease?
The first line treatment for Lyme disease without focal symptoms should be:
For those over 12, oral doxycycline 100 mg twice per day or 200 mg once per day for 21 days.
For those aged 9 to 12, weighing 45kg and under, oral doxycycline 5 mg/kg in 2 divided doses on day 1 followed by 2.5 mg/kg daily in 1 or 2 divided doses for a total of 21 days; for severe infections, up to 5 mg/kg daily for 21 days.
For those under 9, weighing 33kg and under, oral amoxicillin 30 mg/kg 3 times per day for 21 days.
Please see the NICE guideline for more detailed guidance regarding managing Lyme disease and patients presenting with focal symptoms. The BMJ has also produced this great visual summary of the antibiotic treatment used in Lyme disease.
What is the prognosis?
Most patients infected with Lyme disease, who receive prompt and appropriate antibiotic treatment, will go on to recover fully. However, after antibiotic treatment has ended, recovery may continue for months or even years.
- Residual neurological symptoms if treatment was started late in the course of the disease.
- Atrophic lesions, peripheral neuropathy and joint deformities, if acrodermatitis chronica atrophicans caused severe tissue damage.
- In Lyme arthritis, most patients will completely recover from this over several months, but the recovery can be more prolonged in approximately 10% of patients.
How can Lyme disease be prevented?
Keep to marked footpaths and avoid brushing past vegetation
Wear: long sleeves, long trousers and light colours
Use insect repellent containing DEET
Perform tick checks: particularly skin folds and the head, neck and scalp (especially in children)
If a tick is found prompt and correct removal can reduce the risk of Lyme Disease transmission
For more information on tick avoidance and how to remove ticks correctly, please see this patient leaflet from Public Health England.
What should I not be doing?
- Ruling out Lyme disease in patients who have symptoms, but no tick bite
- Diagnosing Lyme disease in patients with a history of a tick bite, but no symptoms
- Ruling out Lyme disease in patients where the clinical suspicion is high, but test results are negative
Not all tick bites cause Lyme disease.
Only around 75% of Lyme disease patients remember having a tick bite.
Only around 60-80% of Lyme disease patients develop erythema migrans.
If a patient presents with erythema migrans, treat them for Lyme disease without further diagnostic testing.
If a patient presents with non-specific symptoms that could be linked to Lyme disease, ask them about recent travel and any activities where they could have been exposed to ticks.
Think Lyme disease! Include it amongst your differentials for patients with non-specific symptoms, even if it is at the bottom of your list.
Longmore M, Wilkinson IB, Baldwin A and Wallin E. Oxford Handbook of Clinical Medicine. 9th edn. OUP 2014.