False Positive Reaction to VDRL Test with Prozone Phenomenon in a Case of Lepromatous Leprosy

Abstract The venereal disease research laboratory (VDRL) test, a nontreponemal test for syphilis, may under a certain set of conditions give false positive results in patients who are not infected with Treponema pallidum. A false positive reaction is defined as a positive reaction to nontreponemal tests, and a negative reaction to treponemal tests, in the serum of a patient who has no history or clinical evidence of syphilis or other treponematosis. A prozone phenomenon in nontreponemal tests is seen largely with secondary syphilis due to high-titer samples that show nonreactive results unless the specimens are diluted. We report here perhaps the first case of lepromatous leprosy, which had a false positive reaction to the VDRL test with the prozone phenomenon. The case initially presented to the outpatient clinic with complaints of epistaxis with nasal stuffiness. The finding of septal perforation on nasal endoscopy is what led to the initial suspicion of syphilis and the subsequent syphilis workup. It was only when the false positive reaction to VDRL test with the prozone phenomenon was noted that the search for other causes was made, which eventually lead to the diagnosis of lepromatous leprosy.