Primary Syphilis

Disease information has been excerpted from VisualDx clinical decision support system as a public health service. Additional information, including symptoms, diagnostic pearls, differential diagnosis, best tests, and management pearls, is available in VisualDx.

Full clinical write-up


Syphilis is a sexually transmitted infection (STI) caused by the spirochete bacterium Treponema pallidum. It is characterized by a chronic intermittent clinical course. Treponema pallidum is transmitted person to person via direct contact with a syphilis ulcer during vaginal, anal, or oral sex and may enter through skin or mucous membranes. Hence, the locations for syphilitic ulcers include the vagina, cervix, penis, anus, rectum, lips, hands, and inside of the mouth.

In the primary stage of syphilis, a painless ulceration, or chancre, typically appears about 21 days after initial infection, often preceded by a firm, painless papule. The chancre is easily seen on the frenulum or on the coronal sulcus of the penis, but it may hide under the foreskin. The chancre may be difficult to observe if located in the vagina or on the cervix. The entire genital area is susceptible, including the anus and inside the urethra. Chancres are typically asymptomatic. If secondary erosion or fissuring occurs, they may be painful. Other symptoms may include bloody stool and rectal pain.

Chancres vary in size from a few millimeters to several centimeters. They have an incubation period of 10-90 days (average 21 days). The chancre lasts 3-6 weeks and heals spontaneously.

Follmann balanitis refers to the rare variant of primary syphilis in men that presents with scattered erosions of the glans and foreskin. A primary chancre may be seen in association or may occur before it presents or after resolution.

All patients with primary syphilis will go on to develop secondary syphilis if the condition is left untreated. Secondary syphilis usually appears 3-10 weeks after the primary chancre and is characterized by a papulosquamous eruption and mucosal involvement in some cases. Tertiary syphilis may appear months to years after secondary syphilis resolves and can involve the central nervous system (CNS), heart, bones, and skin.

Ocular screening (eg, slit lamp examination) is advised for patients with suspected or proven syphilis.

Per the US Centers for Disease Control and Prevention (CDC), the majority of reported male primary and secondary syphilis cases where sex of sex partner is known are among men who have sex with men. An increased incidence of syphilis is associated with HIV positivity.

Immunocompromised patient considerations: Genital ulcers caused by syphilis increase the risk of HIV transmission due to epithelial barrier compromise and increased numbers of macrophages and T-lymphocytes with HIV-specific receptors.

HIV infection can alter the clinical presentation of syphilis. Manifestations include multiple chancres, atypical cutaneous eruptions, increased severity of organ involvement (such as hepatitis and glomerulonephritis), and rapidly developing arteritis and neurosyphilis. Neurosyphilis can occur at any stage of syphilis.

Related topics: ocular syphilisendemic syphilis

Look For:

One or more painless ulcers (chancres) ranging from a few millimeters to several centimeters at the site of inoculation. In men, this site is usually found on the frenulum or coronal sulcus or under the foreskin. In women, this is usually the cervix, vagina, vulva, and/or clitoris. Other potential sites include the lips, oropharynx, hands, perineum, and anus.

The classically described, round, punched-out ulcer is pink, shiny, and has a nonpurulent, clean base with scant serous exudate and an indurated raised border. It is hard and firm in contrast to the soft chancre of chancroid.

The primary chancre typically lasts 10-14 days and clears spontaneously, often without treatment. Bilateral regional lymphadenopathy is very common.

There may be a mixed infection of syphilis with any other STI that may change the appearance of the ulcer. Atypical chancres have been noted to present as painful erosions or ulcers with soft or hard borders with a dirty or clean base. Anal erosions, ulcers, and fissures may also be seen.

Follmann balanitis presents as scattered erosions on the distal penis. They may be confluent with a scalloped border.

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