Overview

Primary syphilis is the first stage of syphilis, a sexually transmitted infection (STI) caused by the bacterium Treponema pallidum. This stage is characterized by the appearance of a painless sore, known as a chancre, at the site where the bacteria entered the body. Primary syphilis develops after exposure through sexual contact, including vaginal, oral, or anal intercourse. Without treatment, syphilis progresses through multiple stages, with primary syphilis being the initial and most identifiable phase. Early diagnosis and treatment during this stage are crucial to prevent further health complications and transmission to others.

Causes

Primary syphilis is caused by infection with the bacterium Treponema pallidum. The main causes and transmission routes include:

• Sexual transmission: The most common mode of transmission is through direct contact with a syphilitic sore during vaginal, anal, or oral sex.
• Contact with open sores: The infection is spread when the bacterium enters the body through tiny cuts or abrasions in the skin or mucous membranes.
• Rare non-sexual transmission: Though extremely rare, transmission can occur through blood transfusion or from mother to baby during childbirth (congenital syphilis).
• High-risk behaviors: Multiple sexual partners, unprotected sex, and men who have sex with men (MSM) are associated with a higher risk of acquiring syphilis.

Symptoms

The hallmark symptom of primary syphilis is the appearance of a single or multiple painless sores (chancres) at the site of infection. Common symptoms include:

• Chancre formation: A round, firm, painless ulcer typically appearing 10 to 90 days after exposure, most commonly within 3 weeks.
• Location of sore: Chancres commonly appear on the genitals, anus, rectum, lips, or mouth, depending on the exposure site.
• Painless nature: Despite being painless, chancres are highly infectious and can go unnoticed, especially when located internally (e.g., vagina or rectum).
• Swollen lymph nodes: Nearby lymph nodes may become swollen and firm.
• Spontaneous healing: The sore typically heals on its own within 3 to 6 weeks, even without treatment; however, the infection persists and progresses.

Diagnosis

Primary syphilis is diagnosed through a combination of physical examination, laboratory tests, and specific serological testing:

• Physical examination: Healthcare providers look for characteristic chancres and lymph node swelling.
• Dark-field microscopy: A sample taken from the chancre can be examined under a microscope to directly detect Treponema pallidum bacteria.
• Serologic tests: Blood tests such as Rapid Plasma Reagin (RPR) or Venereal Disease Research Laboratory (VDRL) are used to detect antibodies against syphilis.
• Treponemal-specific tests: Tests like Fluorescent Treponemal Antibody-Absorption (FTA-ABS) confirm the presence of syphilis-specific antibodies.
• Screening for other STIs: Individuals diagnosed with syphilis are often tested for other sexually transmitted infections, including HIV.

Treatment

Primary syphilis is effectively treated with antibiotics. Early treatment prevents progression to later stages and stops transmission to others. Treatment options include:

• First-line treatment: A single intramuscular injection of benzathine penicillin G is the standard treatment for primary syphilis.
• Alternative antibiotics: For individuals allergic to penicillin, doxycycline or tetracycline may be used as alternatives.
• Partner treatment: Sexual partners should be notified, tested, and treated to prevent reinfection and further transmission.
• Follow-up testing: Repeat serological testing is recommended at 6 and 12 months post-treatment to ensure the infection has been cured.
• Avoid sexual contact: Patients are advised to abstain from sexual activity until the chancre has healed and they have completed treatment.

Prognosis

The prognosis for primary syphilis is excellent with early and appropriate treatment:

• Complete cure: Prompt treatment with antibiotics completely cures the infection in the primary stage.
• Prevention of complications: Early treatment prevents progression to secondary and tertiary syphilis, which can cause severe health problems.
• No long-term effects: If treated early, primary syphilis leaves no lasting effects or damage.
• Risk of reinfection: Having syphilis once does not provide immunity, and reinfection is possible if exposed again.
• Public health importance: Regular STI screening, safe sexual practices, and prompt treatment are key to controlling the spread of syphilis.

With timely treatment, individuals with primary syphilis can expect a full recovery and a return to normal health without complications.