Early dissemination of Borrelia burgdorferi without generalized symptoms in patients with erythema migrans

The diagnosis of erythema migrans (EM) is not always easy, and reports of c ulture- or PCR-confirmed diagnosis as well as reports of EM with simultaneo us disseminated disease are few. Characteristics and incidence of EM in add ition to frequency of early dissemination of B. burgdorferi were studied in the archipelago of South-Western Finland prospectively using questionnaire s, skin biopsies and blood samples. Clinical EM was recognized in 82 patien ts (incidence 148/100000 inhabitants/year). Of skin biopsy samples, 35.5% w ere positive by PCR (the majority B. garinii), and 21.5% by cultivation (ai l B. garinii). Of blood samples, 3.8% were positive by PCR, and 7.7% by cul tivation. Of the patients, 30.9% were seropositive at the first visit, and 52.9% 3 weeks later. Of the patients with laboratory confirmed diagnosis, t he EM lesion was ring-like in 31.8% and homogenous in 65.9%. Dissemination of B. burgdorferi, based on culture or PCR positivity of blood samples, was detected in 11.0% of the patients. The frequency of generalized symptoms w as nearly the same in patients with as in those without dissemination (22.2 % vs 27.4%). Only 21.4% of the patients with culture-positive EM recalled a previous tick bite at the site of the EM lesion. We conclude that EM lesio ns are more often homogenous than ring-like. B. burgdorferi may disseminate early without generalized symptoms.