[Suspected syphilis during pregnancy due to cross reactions in Borrelia infection]

A weakly positive titre (1:20) in the Treponema pallidum haemagglutination test and a highly positive titre (1:1280) in the fluorescence Treponema antibody absorption test, but negative result for IgM antibodies, were found in the serum of a 23-year-old pregnant woman. The cardiolipin microflocculation test was at first borderline positive, but negative on repeat. In the absence of a history of syphilis tests for Borrelia antibodies were performed. Those for antibodies against B. burgdorferi were highly positive in the ELISA test (550 units), in the indirect Borrelia immunofluorescence test 1:1280 for IgG antibodies and 1:160 for IgM antibodies. In the Borrelia-specific indirect haemagglutination test, which measures both IgG and IgM antibodies, the titres were 1:640 to 1:1280. These results confirmed the presence of an infection with B. burgdorferi and not with Treponema pallidum.