Clinical Findings
Signs and Symptoms
The lesions of primary syphilis appear at the site of inoculation after an incubation period that is inversely proportional to the number of infecting organisms, usually 3 weeks (Box 1). The chancre is an ulcerative lesion that varies in size from several millimeters to 2 cm. Although classically described as a solitary lesion, multiple lesions may be present.
They are generally located on the genitalia and anorectal areas, but any area on the body can be affected including the oropharynx and the extremities. This superficial ulcer is usually painless with well-defined, indurated borders surrounding a firm, clean base. Local and regional lymphadenopathy is bilateral, nonsuppurative, painless, and often described as “rubbery.”
Laboratory Findings
Definitive diagnosis can be made by visualization of spirochetes in exudates from these lesions with darkfield or immunofluorescent antibody microscopy. Nontreponemal serologic testing is reactive in 70-80% of patients with primary syphilis but is less sensitive at the time that the chancre first appears. Treponemal antibody tests, specifically the fluorescent treponemal antibody test, are more sensitive during this stage of infection.
Differential Diagnosis
Primary syphilitic genital lesions can be mistaken for lesions associated with trauma, herpes simplex virus, malignancy, chancroid, lichen planus, granuloma inguinale, or lymphogranuloma inguinale. Darkfield examination is helpful in diagnosis. The painful vesicular lesions of herpes are distinguished by multinucleated giant cells when unroofed and examined with a microscope. The ulcerated and nonindurated lesions of chancroid are associated with painful lymphadenopathy. Lymphogranuloma venereum and granuloma inguinale infections are seen primarily in tropical countries.