Syphilis (also known as lues) is a chronic sexually transmitted infection (STI) caused by the spiral-shaped bacterium Treponema pallidum . It enters the body through even the smallest lesions in the mucous membranes or skin. Without treatment, the disease progresses through clearly defined stages and can cause severe organ damage years later. Thanks to modern diagnostics and antibiotic therapy, syphilis is now highly treatable, but case numbers are rising again in many industrialized countries. According to the Robert Koch Institute (RKI) and the WHO , the incidence is increasing particularly among MSM (men who have sex with men) and people with multiple sexual partners.

Historical background

Syphilis was first documented in Europe at the end of the 15th century and, before the introduction of penicillin, was one of the most devastating infections. The later stages led to neurological deficits, personality changes, and heart damage. The discovery of penicillin in the 20th century drastically reduced severe cases; however, changing sexual behavior trends and, in some cases, a decline in the willingness to get tested contribute to a resurgence.

The pathogen

Treponema pallidum is a very fragile bacterium that dies rapidly outside the human body. Therefore, transmission occurs almost exclusively through direct, mostly sexual contact (genital, oral, anal). Rarely, it can occur through blood or during pregnancy (placental transmission to the fetus).

Stage overview

• Primary stage: Painless ulcer (chancre) at the entry point.
• Secondary stage: Systemic spread: skin rashes, mucosal changes, general symptoms.
• Latency: Symptom-free phase – bacteria persist.
• Tertiary stage: Late manifestations (heart, nervous system, granulomatous lesions).

Early diagnosis and therapy effectively stop the progression and prevent long-term consequences.

The symptoms of syphilis vary greatly depending on the stage of the disease. Many affected individuals do not notice early signs or attribute them to other causes. This subtlety facilitates further transmission. A basic understanding of the typical manifestations helps prompt early medical evaluation.

Primary Stage (Chancre)

A single, painless ulcer ("hard chancre") at the site of entry is typical: penis, vulva, anus, mouth, or throat. The edge is often indurated and the center ulcerated, but the lesion often appears unremarkable and is overlooked. Regional lymph nodes are enlarged but not very tender. The ulcer heals spontaneously after 3–6 weeks—this does NOT mean the infection is gone.

Secondary Stage

Weeks to a few months later: generalized skin rash, often on the palms and soles (discrete, reddish-brown macules/papules), mucous patches in the mouth, condylomata lata in the genital/anal area (broad, moist papillomas). Additional symptoms: fever, fatigue, weight loss, lymph node swelling. The wide variety of symptoms makes syphilis "the great imitator."

Latent and Late Stages

In the early latent stage (first year after infection), there are no symptoms, but serology remains positive. Late latency (>1 year) leads, without treatment, to tertiary manifestations in some cases: neurosyphilis (tabes dorsalis, progressive paralysis), cardiovascular syphilis (aortitis), gummatous lesions in skin, bones, and organs. These late forms are rare today but still occur in untreated infections.

Differences by Sex & Special Considerations

In women, primary lesions may be hidden in the vagina or on the cervix. In MSM, extragenital lesions (oral, rectal) are more common. HIV co-infection can accelerate progression or cause atypical skin manifestations. Any unexplained mucosal change or persistent rash should prompt STI testing.

Recommendation: If suspected (unusual ulcer, rash on palms/soles, unclear general symptoms), order a blood test early—the earlier, the simpler the treatment.

Syphilis is primarily transmitted through direct sexual contact. The bacterium enters mucous membranes or skin through micro-injuries. Condoms reduce the risk but do not offer complete protection against lesions outside the covered area.

Transmission paths

• Genital contact: Vaginal or anal intercourse.
• Oral sex: Lesions of the oral mucosa can be infectious.
• Rectal contact: Common in MSM – extragenital lesions often go unnoticed.
• Vertical transmission: From mother to fetus – risk increases with active early syphilis.

risk groups

Increased risk in people with frequently changing partners, men who have sex with men (MSM), sex workers, and people with other STIs (markers of unprotected sex). Coinfections with HIV are more common; syphilis ulcers facilitate HIV transmission through mucosal damage.

Behavioral factors

Irregular testing, failure to notify partners, and the erroneous assumption that spontaneously healed lesions are harmless promote transmission. Substance use (e.g., chemsex scenes) can also increase the risk through prolonged sexual contact with multiple partners.

Biological aspects

Treponema pallidum does not possess classic resistance mechanisms against penicillin; resistance development has not yet been clinically relevant. However, the bacterium evades the immune system through minimal surface antigen variability and persists intracellularly.

Recommendation: Proactive screening strategies (e.g. every 3–6 months in cases of increased risk) reduce long-term consequences and chains of infection.

The diagnosis is based on serology, direct pathogen detection, and clinical findings. Since early lesions are often missed, blood tests play a crucial role. Modern laboratory methods achieve high sensitivity and specificity and allow for stage assessment.

Serological testing strategy

A classic combination of treponemal tests (TPPA/TPHA, FTA-ABS, EIA/CLIA) and non-treponemal tests (VDRL, RPR) is used. Treponemal tests remain positive for life after infection (even after successful treatment), while non-treponemal titers reflect the course of treatment and activity (decline after treatment, increase upon reinfection).

Test window

Seroconversion often occurs 3–6 weeks after infection. Early lesions can be examined for Treponema using dark-field microscopy or PCR – particularly helpful in the primary stage, before antibodies are detectable.

Further diagnostics

• Cerebrospinal fluid examination: In case of suspected neurosyphilis (headaches, neurological deficits) – VDRL in the cerebrospinal fluid + cell count/protein.
• PCR: Direct detection in ulcers or condylomas.
• Point-of-care rapid tests: Initial guidance, laboratory confirmation recommended.

interpretation

A high RPR/VDRL titer (>1:8) indicates active infection; after treatment, the titer decreases within months. Persistently low titers (Serofast) are possible without clinical activity. Reinfection shows a renewed significant increase in titer.

Recommendation: Test early after potential exposure and, if the result is negative, retest after 6 weeks. Notifying partners is essential for containment.

The standard treatment for syphilis is benzathine penicillin G. Its effectiveness has been excellent for decades, and resistance is not an established problem. Early treatment prevents late complications and immediately reduces transmission risks.

Therapy Regimens by Stage

• Early syphilis (primary, secondary, early latency ≤1 year): Single intramuscular dose of 2.4 million IU benzathine penicillin G.
• Late latency or unknown duration: 3 x 2.4 million IU weekly.
• Neurosyphilis: IV penicillin G (e.g., 18–24 million IU/day for 10–14 days) or alternatively ceftriaxone if not tolerated.

Alternatives for Penicillin Allergy

Doxycycline (100 mg twice daily for 14 days for early syphilis) or ceftriaxone can be used. In cases of true severe penicillin allergy with neurosyphilis, desensitization is often recommended (better evidence base).

Jarisch-Herxheimer Reaction

Acute reaction 6–12 hours after first dose: fever, chills, headache, myalgia—resulting from rapid bacterial breakdown. Usually self-limiting within 24 hours. Symptomatic treatment (NSAIDs, fluids) is sufficient.

Therapy monitoring

Serological RPR/VDRL monitoring at 3, 6, and 12 months – a titer drop of at least 4 dilutions is expected (e.g., 1:32 → 1:8). Lack of decline or a rise in titer suggests reinfection or, rarely, treatment failure.

Note: Avoid sexual contact during the first week after treatment, until lesions have healed and infectious secretions are reduced.

Left untreated, syphilis can cause life-threatening complications in its later stages. Thanks to early diagnosis, these manifestations have become less common, but remain a risk if the infection goes undetected or is inadequately treated.

Neurosyphilis

Manifestations range from asymptomatic cerebrospinal fluid changes to tabes dorsalis (destruction of dorsal spinal cord structures: ataxia, radiating pain) and progressive paralysis (dementia, personality changes). Symptoms can appear years to decades after primary infection.

Cardiovascular syphilis

Aneurysms of the thoracic aorta, aortic valve insufficiency, and coronary ostia stenosis due to chronic aortitis are possible. Clinical presentation includes signs of heart failure or thoracic pain.

Gummata

Chronic, granulomatous lesions in the skin, bones, liver, or other organs – destructive, but usually regressive with therapy. Important in differential diagnosis (can resemble tumors).

Pregnancy risks

Miscarriage, stillbirth, congenital syphilis (hepatosplenomegaly, skin lesions, neurological damage). Early screening of all pregnant women (at the beginning, possibly in the 3rd trimester) is recommended according to guidelines.

Psychosocial stress

Stigma and feelings of guilt can negatively impact mental health. Open communication with partners and professional support (doctors, counseling centers) can reduce stress.

Conclusion: Early therapy prevents almost all serious long-term consequences – regular testing is essential for those at risk.

Prevention relies on barrier measures, regular testing, and communication between partners. Since syphilis lesions can also be located outside the condom area, protection is never absolute – however, these measures significantly reduce the risk.

Safer Sex Strategies

• Condoms/Dams: Reduce contact with infectious lesions and secretions.
• Early clarification: Have any unusual lesion medically examined.
• Partner information: In case of diagnosis, inform all relevant sexual contacts (anonymization via partner notification services is possible).

Regular screenings

In cases of increased risk (MSM, frequently changing partners, HIV-positive, chemsex), syphilis serology should be performed every 3–6 months. Combined STI panels (including HIV, gonorrhea, chlamydia, hepatitis) increase efficiency.

Co-infection management

Treating other STIs reduces mucosal inflammation and does not facilitate further transmission. Vaccinations against hepatitis A/B and HPV complement preventive strategies.

Education & Destigmatization

Open, factual discussions reduce shame and encourage early testing. Health portals, counseling centers, and medical education play a key role in this.

Recommendation: A personal screening plan (e.g., calendar entries) prevents forgetting – prevention is active, not passive.

A syphilis diagnosis is treatable and does not mean the end of a fulfilling sex or love life. Information , adherence to treatment , and communication are crucial. Early treatment leads to the elimination of the pathogen and prevents long-term consequences.

Partner communication

Honest, factual language: Syphilis is a bacterial infection like many others – no moral judgment. Recommendations: Time of potential exposure, stage of infection, initiated treatment. Medical records can build trust.

Sexuality after therapy

After treatment is completed and visible lesions have healed, the risk of transmission is greatly reduced. Medical confirmation (antibody titer test) can help if there is any uncertainty. Condoms remain recommended, especially with multiple partners.

Psychological support

In cases of fear or shame: counseling centers, self-help groups, therapists experienced in sexual medicine. The goal is reframing: infections are treatable health events, not character judgments.

Long-term health care

Maintain screening intervals (re-exposure is possible). A healthy lifestyle (sleep, nutrition, stress management) supports the immune system and psychological resilience.

Key message: Knowledge + open communication = secure basis for self-determined sexuality despite a history of illness.

Syphilis during pregnancy poses significant risks to the fetus. Early screening is therefore guideline-based and essential to prevent congenital syphilis.

Risks for the fetus

Untreated early syphilis can lead to miscarriage, stillbirth, or congenital infection (hepatosplenomegaly, skin lesions, skeletal anomalies, neurological damage). The earlier the maternal treatment, the lower the risk.

Screening recommendations

Initial syphilis serology screening at the start of pregnancy, repeat in the third trimester if at risk (high prevalence areas, new sexual partners, clinical suspicion). Positive tests require stage-appropriate penicillin treatment.

Treatment during pregnancy

Benzathine penicillin G is safe and the standard of care. The Jarisch-Herxheimer reaction can trigger uterine contractions – close clinical monitoring is recommended in early stages. Penicillin allergy: Desensitization is preferred (alternatives are less well studied).

Congenital syphilis

Newborns receive a clinical exam, serology (comparison of maternal/neonatal titers), and possibly CSF testing. Early therapeutic intervention prevents irreversible long-term damage.

Important: Prevention starts with consistent testing—syphilis is one of the preventable congenital infections.

Syphilis is surrounded by many persistent myths that contribute to false assumptions and delayed diagnosis. Evidence-based education corrects misinformation.

Myth 1: Spontaneous healing means cure

The primary sore can disappear without treatment—the infection remains and progresses. Serological tests remain essential.

Myth 2: Only "promiscuity" leads to syphilis

Even a single unprotected encounter with an infectious person is enough. Moral judgments are scientifically unfounded and stigmatizing.

Myth 3: Penicillin no longer works

Resistance to benzathine penicillin G is not established—it remains the gold standard. False assumptions lead to unnecessary alternative regimens.

Myth 4: Condoms prevent syphilis 100%

They reduce the risk but do not cover all lesions (e.g., extragenital skin areas). A combination of condoms + screening is more effective.

Conclusion: Informed decisions rely on facts—use objective sources of information (RKI, WHO, ECDC).