Early diagnosis of
Borrelia burgdorferi infection, hampered by the absence of detectable
antibodies in most patients with
erythema chronicum migrans is important to prevent late-stage neurologic, rheumatologic, and skin disorders. Furthermore, B. burgdorferi has been claimed to be the causative agent in
localized scleroderma (
morphea). We used PCR amplification to search for B. burgdorferi outer
surface protein OspA-specific sequences in
DNA obtained from lesional skin biopsies on Finnish patients with clinically suspect
erythema chronicum migrans,
lymphocytoma,
morphea, or with diverse
skin manifestations and persistent high
antibodies to B. burgdorferi flagellar
antigen. Seronegative patients with other skin lesions served as controls. The amplicons obtained with primers specific for B. burgdorferi type strain B31 ospA sequence did not hybridize to the corresponding probes, and thus the
DNA amplified from a Finnish B. burgdorferi
erythema chronicum migrans skin isolate was sequenced. This 98-nucleotide sequence of ospA (332-429) showed 11% to 14%
nucleotide divergence compared with the North American type strain (B31), several European strains, and an East Siberian tick strain. The sequence was almost identical (99%) to a Swedish isolate from
acrodermatitis chronica atrophicans. Using
oligonucleotides specific for the Finnish strain, a positive polymerase chain reaction-based hybridization was obtained in six of seven untreated
erythema chronicum migrans patients infected in Finland or in Estonia, and in the
lymphocytoma patient. Only two of the
erythema chronicum migrans patients had
IgG or
IgM antibodies to
flagellin. However, all seven
morphea lesions as well as the other lesions were polymerase chain reaction negative. Polymerase chain reaction-based hybridization of B. burgdorferi OspA gene from skin-derived
DNA thus provides a sensitive and specific diagnostic tool. In conditions not unequivocally known to be caused by B. burgdorferi, like in
morphea, this assay was negative. We also demonstrate that peri-Baltic B. burgdorferi isolates show homology in their OspA genes but differ from geographically more distant isolates.