Borderline and reactive FTA-ABS. Results in lupus erythematosus.

Fluorescent treponemal antibody absorption tests were performed on serum samples from 43 patients with lupus erythematosus (LE). Seven borderline and three reactive results were obtained from patients who had no evidence of syphilis, and Treponema pallidum immobilization (TPI) tests were nonreactive. These probable nonsyphilitic reactions were associated with discoid LE (DLE) as frequently as with systemic LE (SLE). Three of these serum samples were reactive in the microhemagglutination assay for T pallidum antibodies (MHA-TP), but titers were low. Reactive FTA-ABS tests were also obtained from four patients with LE with evidence of syphilis. All four serum samples were highly reactive in the MHA-TP test. These findings suggest that nonsyphilitic FTA-ABS fluorescence is (1) common with both DLE and SLE, (2) frequently not "beaded" in pattern, and (3) often detectable when MHA-TP tests are performed.