Thirty patients with different clinical manifestations of morphea (circumscribed scleroderma) were investigated for serum antibodies against Borrelia burgdorferi determined by ELISA and Western blot analysis. Forty-six percent of the patients were seropositive. Western blots confirmed the ELISA results in 10 of 25 patients (40%), showing a reactivity pattern which can be seen in the course of
Lyme borreliosis. In some cases the outcome after antibiotic treatment suggests a direct correlation between the further development of skin lesions and Borrelia infection. Because of these findings we suggest some morphea types to be possibly due to a B. burgdorferi infection.