Syphilis

Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum subspecies pallidum. It can present in four stages: primary, secondary, latent, and tertiary, each with distinct clinical features. Additionally, syphilis can be transmitted from mother to baby, resulting in congenital syphilis.

Signs and Symptoms

Primary

Primary syphilis typically presents 2–6 weeks after exposure with a chancre at the site of infection. This lesion is usually a single, firm, painless, non-itchy skin ulcer. Lymph node enlargement around the area of infection is common.

Secondary

Secondary syphilis occurs approximately 4–10 weeks after the primary infection. It is known for its varied manifestations, most commonly a symmetrical, reddish-pink, non-itchy rash on the trunk, extremities, palms, and soles. Other symptoms include fever, sore throat, malaise, weight loss, hair loss, and headache.

Latent

Latent syphilis has no symptoms but is detectable by serology. It is divided into early latent (within 2 years of infection) and late latent (after 2 years). Early latent syphilis can still be infectious.

Tertiary

Tertiary syphilis may occur 3 to 15 years after the initial infection and manifests in three forms: gummatous syphilis, late neurosyphilis, and cardiovascular syphilis. Gummatous syphilis involves chronic gummas, which are inflammatory tumours. Cardiovascular syphilis often results in aortic aneurysm formation. Neurosyphilis can lead to stroke, dementia, and other severe neurological symptoms.

Congenital

Congenital syphilis can present with a range of symptoms in infants, including liver and spleen enlargement, rash, fever, neurosyphilis, and lung inflammation. If untreated, it can lead to severe deformities such as saddle nose, sabre shin, and Hutchinson's teeth.

Cause and Transmission

Treponema pallidum is a spiral-shaped, Gramme-negative bacterium that is highly mobile. It is primarily spread through sexual contact or from mother to baby during pregnancy. It can also be transmitted through kissing near a lesion and sharing needles, although these are less common modes of transmission.

Diagnosis

Syphilis is diagnosed using blood tests and direct visual inspection. Blood tests include nontreponemal tests (VDRL, RPR) and treponemal tests (Treponema pallidum particle agglutination assay, FTA-Abs). Dark field microscopy of serous fluid from a chancre can also be used for immediate diagnosis.

Treatment

Early Infections

The first-line treatment for early syphilis is a single dose of intramuscular benzathine benzylpenicillin. Alternatives for those allergic to penicillin include doxycycline and tetracycline. Ceftriaxone may also be effective. Patients should avoid sexual activity until sores are healed.

Late Infections

Neurosyphilis requires large doses of intravenous penicillin G. For other late presentations, intramuscular benzathine penicillin is administered weekly for three weeks.

Jarisch–Herxheimer Reaction

A potential side effect of treatment is the Jarisch–Herxheimer reaction, which includes fever, muscle pains, headache, and a fast heart rate. It occurs due to cytokines released by the immune system in response to rupturing syphilis bacteria.

Epidemiology

Syphilis remains a significant public health problem globally. In 2015, about 45.4 million people had infections, causing around 107,000 deaths. Rates have been increasing in many countries since the early 2000s, often in conjunction with HIV. Men who have sex with men are particularly affected.

---

Self-assessment MCQs (single best answer)

What bacterium causes syphilis?

Which stage of syphilis is characterised by a chancre at the site of infection?

In secondary syphilis, where is the rash most commonly found?

What is the main treatment for early syphilis?

Which stage of syphilis is characterised by chronic gummas?

What is a Jarisch–Herxheimer reaction?

Which diagnostic method involves the use of dark field microscopy?

Which symptom is NOT typically associated with secondary syphilis?

How is syphilis most commonly transmitted?

Which population is particularly affected by increasing syphilis rates?