Atypical Oral Mucosal Lesions in Syphilis: A Case Report Highlighting the Diagnostic and Therapeutic Aspects of the "Great Imitator".

The diagnostic process and discrimination of mucosal lesions present a formidable challenge for numerous clinicians, primarily attributable to the common overlap of clinical manifestations observed across various categories, including infectious, autoimmune, connective tissue, and systemic vascular inflammatory diseases. In cases of mucosal lesions, syphilis presents distinctive characteristics that can help clinicians differentiate it from other conditions. The most common manifestation of primary syphilis is mostly a painless, firm, indurated ulcer known as a chancre, which typically appears at the site of inoculation, with enlargement of regional lymph nodes. Sometimes, its painless course may be misleading. The objective of our study is to raise awareness of venereal diseases in cases of atypical oral mucosal lesions that do not respond to local treatment. A 32-year-old man was referred to the department of dermatology due to an enlarging, painful inflammatory lesion with central breakdown, covered with honey-yellow crusts on the lower lip. A positive history of herpes labialis was noted. The patient denied risky sexual behaviors or new partners in the last three months. Submandibular and left cervical lymph nodes were found enlarged in ultrasound examination, and laboratory tests showed elevated inflammatory parameters. Empirical antibiotic therapy with amoxicillin-clavulanate in conjunction with oral acyclovir did not lead to clinical improvement. The inadequate therapeutic response prompted the pursuit of further diagnostic investigations, including serological tests encompassing both treponemal and nontreponemal tests. Co-infections with human immunodeficiency virus (HIV) and hepatotropic viruses were excluded. The serological testing resulted positive, and after receiving the diagnosis, the patient admitted to engaging in high-risk sexual behaviors. The treatment with benzathine penicillin was successful. In the differential diagnosis of ulcers located on mucous membranes or vermilion border, the primary symptom should always be considered. Early serological testing remains the gold standard for diagnosis. Appropriate treatment with benzathine penicillin leads to satisfactory effects.