The majority of suggested mechanisms of Borrelia spreading inside erythema migrans (EM) are developed from in vitro studies and animal models. This report is the first to describe pathomorphological substrate of EM caused by Borrelia spielmanii in humans, addressing the hypothesis of enhanced Borrelia penetration through extracellular matrix. In the process of ruling out of atypical Masters' disease, we conducted a punch biopsy of suspected EM and a two-tier serology testing for Lyme borreliosis, where we registered antibodies against B. spielmanii. Skin biopsy showed CD4+ and CD8+ lymphocyte involvement and high activity of matrix metalloproteinase 9. No alterations were detected in distribution and morphology of collagen type I and IV. Therefore, it is suggested that other mechanisms should be considered as major contributing factors to local spreading of B.spielmanii.
Keywords: B. spielmanii; Borrelia; MMP9; collagen type I; collagen type IV; erythema migrans; lyme borreliosis.