An unusual pattern of treponemal fluorescence was found when the flourescent treponemal antibody-absorption (FTA-ABS) test was performed on serum samples from four presumably nonsyphilitic patients with active systemic lupus erythematosus. Instead of the homogeneous fluorescence of the Treponema pallidum organisms seen with serum samples from patients with syphilis, a "beaded" fluorescence was observed. Since the intensity of the atypical fluorescence was comparable to that seen with serum samples from patients with syphilis, if the atypical nature of the fluorescence had not been noted, the test result may have been reported reactive. Such reactive test results could lead to an erroneous diagnosis of syphilis.
Kraus SJ, Haserick JR, Lantz MA. Atypical FTA-ABS Test Fluorescence in Lupus Erythematosus Patients. JAMA. 1970;211(13):2140–2141. doi:10.1001/jama.1970.03170130036007