Mini erythema migrans--a sign of early Lyme borreliosis.

BACKGROUND: An erythema migrans (EM) remaining smaller than 5 cm in diameter, called mini EM by us, has not been addressed in detail.

OBJECTIVE: To study the significance of the mini EM as a sign of Lyme borreliosis.

METHODS: Patients with suspected mini EM were retrospectively selected out of 257 consecutive patients with EM. The diagnosis of mini EM rested on the cultivation of Borrelia burgdorferi. Species and subtype analysis of culture isolates was performed using outer surface protein A (OspA) polymerase chain reaction followed by restriction fragment length polymorphism and sequencing of the OspA gene.

RESULTS: There was one patient with definite (0.4%) and another patient with a questionable mini EM. Borrelia garinii OspA type 6 was identified in the patient with the definite and B. burgdorferi sensu lato in the patient with the questionable mini EM.

CONCLUSION: The mini EM represents an important and apparently uncommon sign of early Lyme borreliosis.