THE CHALLENGING DIAGNOSIS OF SERONEGATIVE ORAL SYPHILIS IN AN HIV-INFECTED PATIENT

Abstract

<h3>Background</h3> In people living with HIV/syphilis-coinfection, overlapping of clinical stages and misleading anti-treponemal serologic tests have been described. This is the report of serological (false-negative) non-reactive, polymerase chain reaction (PCR)-confirmed syphilis in an HIV-infected patient. <h3>Case Description</h3> An HIV-infected male patient, 28-years-old, receiving antiretrovirals (TDF/FTC/DTG) with therapeutic success (CD4: 667 cells/mm³, undetectable HIV-plasma viral load), was referred to our Oral Pathology & Medicine Service in Mexico City. A 3-month asymptomatic ulcerated lesion on the right side of the soft palate and anterior pillar, with granular appearance, irregular borders, and measuring 2 to 3 cm in diameter, was observed. A painless, right cervical lymph node was present. A quantitative serum Venereal Disease Research Laboratory (VDRL) assay was nonreactive (serum was diluted 6-fold to rule out a prozone phenomenon and remained negative). Histopathologic analysis revealed an intense mixed inflammatory infiltrate; differential diagnosis included secondary syphilis, lymphoproliferative disorder, and deep mycotic infection. The immunohistochemistry (IHC) for <i>T. pallidum</i> was negative. DNA extraction was performed, and the <i>T. pallidum</i> gene polA was amplified by PCR; as a consequence, the patient received benzathine-penicillin G (2.4 million units) single dose. VDRL and treponemal FTA-abs were done twice, with negative results. A new biopsy revealed positive IHC<i>-T. pallidum</i>. Two months later, a mucous patch appeared on the tonsillar pillar, with histopathologic features of secondary syphilis and positivity for IHC-<i>T. pallidum</i>. VDRL and FTA-abs assays remained non-reactive. Oral lesions resolved after 3 doses of benzathine-penicillin G. <h3>Conclusions</h3> In absence of serological evidence, the diagnosis of oral syphilis is a challenge. PCR and IHC may represent supplementary helpful diagnostic tools.