Exposing the Great Imitator: Proposal for a Holistic Diagnosis of Oral Secondary Syphilis in People Living with HIV.

Oral secondary syphilis may mimic various infectious, neoplastic, or immune-mediated processes; hence, its diagnosis may represent a challenge. Early diagnosis of syphilis, a disease that has increased in recent decades, is essential for adequate management, particularly in people living with HIV (PLWH). This study aimed to comprehensively characterize oral secondary syphilis in a group of 47 PLWH. A group of PLWH with oral secondary syphilis attending four HIV-referral centers in Mexico City was included (2004-2021). Clinical and laboratory data were retrieved, and an exhaustive oral examination was performed following the established criteria. Demographic, clinicopathological, immunohistochemical, and serological features of the patients were analyzed. Approximately 11% of PLWH with oral secondary syphilis demonstrated negative Venereal Disease Research Laboratory tests. A noticeable feature was the absence of symptoms in 95.7% of cases, despite the clinically evident appearance of the lesions. In contrast to previous results, 18% of ulcerations were detected to be deep, crateriform, and infiltrative, and 22% of the mucous patches were highly keratotic lesions. Most samples (77.3%) showed superficial lymphoplasmacytic infiltrates in the superficial lamina propria, with perivascular and perineural patterns, and immunohistochemistry was positive in 66.7% of the cases. The "great imitator" appears not only clinically but also histopathologically and immunohistochemically, where features may be comparable with those of chronic inflammatory processes, deep infections, or malignant processes. Although not recommended as a routine assay, IHC could be a critical tool, particularly in PLWH with atypical clinical features or with negative and/or dubious serology.