This is a characteristic clinical feature of Lyme borreliosis, occurring in approximately 90% of patients infected with Borrelia burgdorferi transmitted to humans by the bite of ticks from the genus Ixodes.

Epidemiology

• Lyme disease occurs in temperate regions of North America, Europe and Asia.
• In some countries of Europe the incidence of Lyme disease has been estimated to be over 100 per 100,000 people a year.

Presentation¹

• The characteristic manifestation of early Lyme disease (stage 1) is erythema migrans: a circular rash at the site of the infectious tick attachment, which radiates from the bite, within 2-40 days.
• It starts as a red macule or papule at the site of the tick bite after a 7- to 10-day delay.
• Common areas include the popliteal fossa, groin, the axilla, the thorax and the trunk The hairline and scalp are especially common in children.
• It is associated with other symptoms of infection, including fatigue, myalgia, arthralgia, headache, fever, chills, stiff neck, and regional lymphadenopathy.
• It is also associated with carditis, neurological disease, arthritis, and acrodermatitis chronica atrophicans (a swollen, bluish-red skin lesion on a distal extremity).

Differential diagnosis

• Local tick bite reactions
• Tinea
• Insect bites
• Cellulitis
• Dermatitis

Investigations¹

• Culture, serology and skin biopsy may be necessary for diagnosis.

Management

Although the rash will resolve spontaneously, antibiotics hasten resolution and help prevent progression to Lyme disease:

• Doxycycline is the antibacterial of choice for early Lyme disease.²
• Amoxicillin or cefuroxime are alternatives if doxycycline is contra-indicated.
• Macrolides such as azithromycin or clarithromycin should be reserved as third-line treatment as they are not as effective as the aforementioned antibiotics.³
• The duration of treatment recommended is 2-4 weeks.

Prevention

• Avoid exposure to tick bites.
• Antibiotic prophylaxis can be offered in endemic areas under certain circumstances if the tick bite can be positively identified.³

Document references

1. Edlow J; Erythema Chronicum Migrans, eMedicine, May 2010
2. British National Formulary
3. Wormser GP, Dattwyler RJ, Shapiro ED et al.; The clinical assessment, treatment, and prevention of lyme disease, human granulocytic anaplasmosis, and babesiosis: clinical practice guidelines by the Infectious Diseases Society of America. Clin Infect Dis. 2006 Nov 1;43(9):1089-134. Epub 2006 Oct 2.

Internet and further reading

• Erythema chronicum migrans, DermIS, Dermatology Information System

Acknowledgements