Visual Diagnosis

Case: A 3-year-old boy presents with a rash that started after camping in the woods near his home with his family 1 week prior. What is the diagnosis?

Diagnosis:

This patient has erythema migrans.

Erythema migrans is the most common clinical manifestation of Lyme disease, and the most common manifestation in pediatric patients.¹ In the United States, the bite of the Ixodes scapularis tick (Northeastern and upper Midwest regions) or the Ixodes pacificus tick (Pacific coast region) transmits Borrelia burgdorferi, the cause of this disease.² Lyme disease is classified into 3 stages: (1) early localized, (2) early disseminated, and (3) late stage. Erythema migrans is a dermatologic manifestation of early localized disease.

Clinical Practice Pearls:

• The appearance of erythema migrans alone is adequate for clinical diagnosis and initiation of treatment without laboratory confirmation of Lyme disease.
• The rash usually appears between 7 and 14 days after a tick has detached.² The initial appearance is a painless red macule or papule, that later expands to form a large, erythematous annular lesion, occasionally accompanied by partial central clearing, with a diameter of at least 5 cm.¹ There is no associated pruritus, and the central area may appear vesicular or necrotic.¹
• Hypersensitivity reactions can be seen while the tick is attached or within 48 hours of the tick becoming detached. These lesions are < 5 cm in diameter, have an urticarial appearance, and begin to disappear within 1 to 2 days.²
• Associated symptoms are not uncommon and may include fever, malaise, headache, neck stiffness, myalgias, and arthralgias.³
• Antibiotic therapy for pediatric patients can be amoxicillin or cefuroxime axetil. Doxycycline maybe used in patients aged > 8 year, but should be avoided in pregnant or lactating patients. Macrolides are not recommended as first-line therapy.

Additional Reading:

1. American Academy of Pediatrics. Lyme Disease. Red Book Atlas of Pediatric Disease. 2^nd ed. Elk Grove Village, IL. Chapter  77. American Academy of Pediatrics, 2013. 
2. 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; 43(9):1089-1134.
3. Mukkada S, Buckingham SC. Recognition and prompt treatment for tick-borne infections in children. Infect Dis Clin N Am. 2015 Jul 16. pii: S0891-5520(15)00049-5. doi: 10.1016/j.idc.2015.05.002. [Epub ahead of print]