Clinical Guides
Syphilis
A clinically focused guide to syphilis staging, test interpretation, penicillin regimens, pregnancy, neurosyphilis, partner services, follow-up and NACO-linked care in India.
MedNext Academy | 12 min read
Syphilis
A clinically focused guide to syphilis staging, test interpretation, penicillin regimens, pregnancy, neurosyphilis, partner services, follow-up and NACO-linked care in India.
Summary
Syphilis is a sexually transmitted infection caused by Treponema pallidum, with stages that may be clinically silent and can involve the nervous system, eye or ear at any time. Diagnosis joins symptoms and examination with a nontreponemal test such as RPR or VDRL and a treponemal test such as TPPA, TPHA or an enzyme immunoassay. One reactive test alone does not reliably establish active infection or stage. A fourfold change in the same nontreponemal test is the meaningful serological change for follow-up.
Benzathine penicillin G remains the treatment of choice for uncomplicated early and late latent infection; regimens differ by stage and neurosyphilis or ocular disease requires aqueous crystalline penicillin in hospital. Pregnancy requires penicillin because no proven alternative prevents congenital infection; a reported allergy needs validated evaluation and desensitisation, not substitution. Warn about the Jarisch–Herxheimer reaction, notify and test partners, screen for HIV and other STIs, and arrange stage-appropriate serology. This India-focused educational draft is has been reviewed by the MedNext Clinical Team and is not a personal diagnosis or prescription. Reassess the person rather than treating a laboratory label in isolation: document stage uncertainty, explain confidentiality and partner care, and arrange a time-bound review with clear escalation advice.
How Common Is It?
Syphilis notification reflects true infection, access to testing, screening of pregnancy and key populations, partner services, and reporting quality. A low number in one district does not prove low transmission. Infection can be missed during latent stages, and lesions may be hidden or absent. Indian programmes therefore combine facility-based STI services, antenatal screening and targeted prevention rather than relying on symptomatic attendance alone.
Transmission is most efficient during primary, secondary and early latent infection, but untreated disease can persist for years. Congenital syphilis is preventable when antenatal screening and timely penicillin are available. Ask about previous results and treatment because treponemal tests often remain reactive for life. A positive screen may represent old treated infection, untreated infection or a false-positive result; the burden cannot be inferred from a single reactive card test.
Services should monitor time from antenatal booking or presentation to testing, treatment, partner notification, documented follow-up and congenital outcomes. Confidentiality is essential, particularly where stigma or violence is possible. Use NACO-linked STI/RTI services and referral networks where available. Epidemiology supports active case-finding and prevention, but each patient still needs stage assessment and a documented treatment history. Reassess the person rather than treating a laboratory label in isolation: document stage uncertainty, explain confidentiality and partner care, and arrange a time-bound review with clear escalation advice.
Risk Factors
Risk increases with condomless sex, multiple or overlapping partners, a partner with a diagnosed STI, previous syphilis, HIV or other STI, sexual networks with high transmission, and barriers to testing or partner treatment. Men who have sex with men, transgender people, sex workers, people who inject drugs and people in correctional or other high-exposure settings may face disproportionate burden, but stigma must never be used as a diagnosis. Anyone with a compatible lesion or sexual exposure can have syphilis.
Pregnancy is a special risk context because untreated maternal infection can cause miscarriage, stillbirth, prematurity, hydrops or congenital disease. Ask about antenatal testing, prior treatment, gestational age and partner treatment. Neurological, ocular or otic symptoms can appear at any stage. Immunosuppression may alter presentation, but HIV status does not replace ordinary stage assessment.
Take a nonjudgmental sexual history: sites of contact, timing, condom use, partners, prior tests, treatment and symptoms in partners. Risk assessment guides testing and public-health action; it should not be used to deny testing to someone without a stereotyped risk factor. Record allergy history carefully, distinguishing anaphylaxis from predictable injection reactions, because penicillin is uniquely important in pregnancy. Reassess the person rather than treating a laboratory label in isolation: document stage uncertainty, explain confidentiality and partner care, and arrange a time-bound review with clear escalation advice.
Diagnosis
History
Ask about a painless ulcer, rash including palms and soles, mucous patches, condylomata lata, fever, lymphadenopathy, patchy alopecia, visual change, hearing symptoms, headache, cranial-nerve symptoms or cognitive change. Establish onset, sexual sites, pregnancy, prior syphilis tests and exact treatment, partner exposure, HIV risk and other STI symptoms. A chancre may have healed before presentation; absence of a lesion does not exclude infection.
Examination
Inspect oral, genital, perianal and skin sites with consent, including palms, soles and lymph nodes. Look for neurologic deficits, meningism, eye inflammation or reduced vision and hearing abnormalities. Examine every pregnant patient with a reactive screen for clinical evidence but do not wait for signs before treatment. Document lesion morphology and photograph only with consent and secure governance. Consider differential diagnoses such as herpes, chancroid, aphthae, psoriasis, pityriasis rosea and drug eruption.
Investigations
Use a quantitative RPR or VDRL plus a treponemal assay, following the local algorithm. If tests disagree, obtain a second treponemal test using a different method. A reactive treponemal test usually persists; a low RPR can be old infection, early infection, late infection or a false positive. Compare the same test and laboratory for follow-up. Test for HIV, hepatitis B and C and other locally indicated STIs. Suspected neurosyphilis requires specialist assessment and CSF studies; ocular or otic disease needs urgent specialist examination and is treated as neurosyphilis even if CSF is normal. Reassess the person rather than treating a laboratory label in isolation: document stage uncertainty, explain confidentiality and partner care, and arrange a time-bound review with clear escalation advice.
Differential Diagnosis
A genital or oral ulcer may be herpes, chancroid, lymphogranuloma venereum, donovanosis, trauma, aphthosis, Behçet disease or malignancy. A rash of secondary syphilis can resemble pityriasis rosea, psoriasis, viral exanthem, drug eruption or acute HIV. Condylomata lata are broad moist lesions and differ from anogenital warts caused by HPV. Reactive serology can reflect treated infection, early infection before full seroconversion, late infection, cross-reactivity or a biological false-positive RPR.
In endemic settings, yaws and other treponemal infections may complicate interpretation, particularly when a treponemal test is positive and sexual history is not explanatory. A reactive test does not itself identify stage or prove that current symptoms are syphilis. Conversely, early primary disease can have negative serology; if suspicion is high, repeat testing and specialist review are appropriate. Dark-field or lesion PCR availability is limited and a negative result does not automatically exclude disease.
Neurological or visual symptoms must not be explained away as anxiety or a benign rash. Malignancy, HIV-associated disease and ocular inflammation remain important alternatives. Use an integrated clinical and laboratory assessment, document uncertainty, treat when the risk of delay is substantial, and arrange follow-up to resolve discordant results. Reassess the person rather than treating a laboratory label in isolation: document stage uncertainty, explain confidentiality and partner care, and arrange a time-bound review with clear escalation advice.
Management
Treat according to documented or most likely stage. Primary, secondary and early latent syphilis are treated with benzathine penicillin G 2.4 million units intramuscularly once. Late latent syphilis or syphilis of unknown duration requires benzathine penicillin G 2.4 million units IM weekly for three doses (7.2 million units total); if a dose is substantially delayed, specialist advice is needed and the series may need restarting. Do not substitute oral penicillin.
Neurosyphilis, ocular syphilis and otosyphilis require urgent specialist and often inpatient care with aqueous crystalline penicillin G 18–24 million units per day, given as 3–4 million units IV every four hours or continuous infusion for 10–14 days, according to local protocol. Aqueous treatment is required even when ocular symptoms occur without CSF abnormalities. Congenital syphilis needs paediatric expertise. In pregnancy, use the stage-appropriate penicillin regimen; if allergy is credible, desensitise and treat in a monitored setting.
Abstain from sex until lesions have healed, treatment is complete as advised and partners have been assessed. Treat partners based on exposure and stage guidance. A Jarisch–Herxheimer reaction is common within 24 hours; it is not penicillin allergy. Provide antipyretic advice and urgent warning signs. Record batch, dose, site, dates and follow-up plan. Reassess the person rather than treating a laboratory label in isolation: document stage uncertainty, explain confidentiality and partner care, and arrange a time-bound review with clear escalation advice.
Prescribing Information
Benzathine penicillin G is a deep intramuscular preparation and must never be given intravenously or confused with aqueous penicillin. Verify the formulation, dose, expiry, allergy history, pregnancy status, stage, weight where relevant, and emergency equipment before administration. Use a trained clinician and observe for immediate anaphylaxis according to local policy. Do not use a single dose for late latent or unknown-duration infection simply because symptoms are absent.
For late latent treatment, schedule doses seven days apart. In pregnancy, an interval longer than the accepted window can compromise the series; contact obstetric/infectious-disease services rather than improvising. If neurosyphilis or ocular disease is suspected, do not delay referral while arranging an outpatient benzathine injection; it does not achieve therapeutic CSF concentrations. HIV infection generally does not change the recommended penicillin regimen, but follow-up must be reliable.
Separate true immediate allergy from nausea, pain or a vasovagal event. There is no validated alternative that reliably prevents congenital syphilis, so pregnant patients with confirmed allergy require desensitisation followed immediately by penicillin. Document the product and route, counselling, partner plan, RPR titre and next test. Check for interactions and coexisting STI treatment. Penicillin supply and trained administration may vary in India; arrange a complete course before the patient leaves. Reassess the person rather than treating a laboratory label in isolation: document stage uncertainty, explain confidentiality and partner care, and arrange a time-bound review with clear escalation advice.
When to Refer
Refer urgently for reduced vision, eye pain or redness, hearing loss, tinnitus with neurologic features, cranial-nerve palsy, meningism, focal weakness, altered cognition, severe headache, ataxia or suspected aortic or gummatous complications. Ocular and otic syphilis are managed as neurosyphilis with specialist examination and aqueous penicillin. Refer newborns or pregnant patients with reactive tests promptly to obstetric, infectious-disease and paediatric services.
Refer for penicillin allergy in pregnancy, uncertain stage with complex prior treatment, persistently rising titres, suspected treatment failure, reinfection, HIV with poor follow-up, discordant serology, suspected congenital infection or inability to deliver monitored injections. A sexual-health clinic can assist with partner notification, confidential testing, contact tracing and violence-sensitive prevention. NACO STI/RTI services and integrated counselling and testing centres may provide local referral routes.
Emergency transfer is appropriate for anaphylaxis, severe ocular symptoms or neurologic deterioration. Give the receiving team test types and titres, symptoms, prior regimens and dates, pregnancy and HIV status, last dose and partner actions. In India, do not assume every facility stocks benzathine or aqueous penicillin; confirm availability and transport safely. Referral should preserve confidentiality and ensure the patient is not lost between laboratory, antenatal and STI services. Reassess the person rather than treating a laboratory label in isolation: document stage uncertainty, explain confidentiality and partner care, and arrange a time-bound review with clear escalation advice.
Red Flags
Visual loss, eye pain, uveitis, new hearing loss, facial weakness, meningism, focal neurologic deficit, confusion, ataxia, severe headache or stroke-like symptoms suggest ocular or neurosyphilis and require urgent assessment. A pregnant person with a reactive test, absent treatment documentation, a high or rising titre, symptoms, or a partner with untreated infection needs same-day linkage to treatment. Newborn rash, snuffles, hepatosplenomegaly, jaundice, anaemia, bone tenderness or neurologic signs require congenital-syphilis evaluation.
Anaphylaxis after penicillin—wheeze, throat swelling, hypotension, collapse or widespread urticaria—is an emergency; distinguish it from the painful injection, vasovagal faint and transient fever of a Jarisch–Herxheimer reaction. Severe fever or contractions after treatment in pregnancy still need obstetric advice, because the reaction can affect fetal monitoring.
A fourfold or greater rise in RPR/VDRL titre, recurrent lesions or new symptoms suggests reinfection or treatment failure. Failure to attend the next weekly dose, a dose outside the permitted interval, no partner action, or no documented follow-up is a system red flag. Do not reassure from a persistent treponemal test alone; interpret it with the quantitative nontreponemal result and treatment history. Reassess the person rather than treating a laboratory label in isolation: document stage uncertainty, explain confidentiality and partner care, and arrange a time-bound review with clear escalation advice.
Indian Clinical Context
NACO's STI/RTI programme provides an important public-health framework for syndromic care, laboratory linkage, prevention, counselling and partner services, while current WHO and CDC guidance supplies stage-specific diagnostic and treatment detail. Local protocols and medicine availability must be checked because facility-level testing, RPR access, benzathine stock, cold-chain storage and trained injection staff vary. A card test without confirmatory or quantitative follow-up should not be treated as a complete lifelong record.
Offer confidential HIV testing and other STI screening with consent, and link reactive results to integrated counselling and testing services. Antenatal screening should happen early enough for treatment to protect the fetus; repeat testing follows local risk and programme guidance. Use culturally safe language, avoid moralising, and consider intimate-partner violence before contacting partners. Record partner notification without exposing the index patient's identity.
For patients travelling between districts, provide a paper or digital treatment record with test type, titre, stage, drug, dose, route and dates. Confirm the next injection site before discharge. Do not substitute doxycycline in pregnancy, or assume an oral course covers neurosyphilis. NACO, WHO and NMC resources should be read alongside state STI protocols and specialist advice. This draft is educational, clinically focused and has been reviewed by the MedNext Clinical Team. Reassess the person rather than treating a laboratory label in isolation: document stage uncertainty, explain confidentiality and partner care, and arrange a time-bound review with clear escalation advice.
NMC Competency Mapping
Syphilis maps to NMC competencies in Dermatology, Venereology, General Medicine, Obstetrics and Gynaecology, Paediatrics, Pharmacology, Microbiology, Psychiatry and community medicine. Learners should take a respectful sexual and treatment history, examine lesions and rash distribution, recognise primary, secondary and latent patterns, interpret paired treponemal and nontreponemal tests, stage disease and identify neurologic or ocular emergencies.
Pharmacology outcomes include benzathine versus aqueous penicillin, route safety, weekly dosing, allergy evaluation, desensitisation, the Jarisch–Herxheimer reaction and pregnancy-safe prescribing. Obstetric learning includes antenatal screening, prevention of congenital syphilis and coordinated treatment. Microbiology includes antibody kinetics, persistent treponemal reactivity and a meaningful fourfold RPR/VDRL change. Community medicine includes confidentiality, partner notification, contact tracing, HIV/STI integration and NACO programme pathways.
Assessment can use an OSCE on counselling for a reactive RPR, a laboratory-interpretation station with discordant tests, a pregnancy allergy scenario and an emergency handover for ocular syphilis. Exam answers should state that stage determines regimen and that a treponemal test is not a test of cure. Institutions should map learning to the current CBME curriculum; this guide does not authorise independent treatment. Reassess the person rather than treating a laboratory label in isolation: document stage uncertainty, explain confidentiality and partner care, and arrange a time-bound review with clear escalation advice.
Key Exam Pearls for NEET PG
Primary syphilis classically causes a painless chancre; secondary disease causes a widespread rash that may involve palms and soles; latent disease has no symptoms. A reactive treponemal test usually remains positive for life, while RPR or VDRL titres support activity and response. Use a fourfold change, such as 1:32 to 1:8, rather than a one-dilution fluctuation to judge a meaningful difference, ideally with the same test and laboratory.
Benzathine penicillin G 2.4 million units IM once treats primary, secondary and early latent disease. Late latent or unknown-duration disease receives 2.4 million units IM weekly for three weeks. Neurosyphilis, ocular and otic disease require aqueous crystalline penicillin G IV for 10–14 days and urgent specialist care. Pregnancy requires penicillin; allergy means desensitisation, not doxycycline. A Jarisch–Herxheimer reaction is fever and worsening symptoms soon after treatment, not IgE allergy.
Always test for HIV and offer partner services. A fourfold titre rise or recurrent symptoms suggests reinfection or failure. Congenital syphilis is preventable through antenatal screening and timely maternal treatment. Do not stage from a single test, use benzathine for CNS disease, or call a persistent treponemal result treatment failure. Reassess the person rather than treating a laboratory label in isolation: document stage uncertainty, explain confidentiality and partner care, and arrange a time-bound review with clear escalation advice.
Frequently Asked Questions
Does a positive treponemal test prove current untreated syphilis infection?
No. Treponemal tests commonly remain reactive after adequate treatment and cannot stage disease alone. Interpret them with a quantitative RPR or VDRL, symptoms, prior treatment records and, when discordant, a second treponemal method and specialist advice. The decision should be recorded with stage, test titres, pregnancy status, partner support and a written follow-up plan.
What penicillin regimen is used for late latent syphilis in adults?
Benzathine penicillin G 2.4 million units intramuscularly weekly for three doses is the standard pathway for late latent infection or unknown duration. Dose intervals matter; a substantially delayed dose needs specialist review rather than an improvised extra injection. The decision should be recorded with stage, test titres, pregnancy status, partner support and a written follow-up plan.
What if a pregnant patient reports a penicillin allergy?
Confirm the history and involve obstetric, infectious-disease or allergy services. Penicillin is the treatment with evidence to prevent congenital syphilis, so a credible allergy requires monitored desensitisation followed by the appropriate penicillin regimen. Do not substitute doxycycline. The decision should be recorded with stage, test titres, pregnancy status, partner support and a written follow-up plan.
How is the Jarisch–Herxheimer reaction different from true penicillin allergy?
It is a transient fever, chills, headache, myalgia or symptom flare, usually within 24 hours of treatment, caused by inflammatory response to treponemal killing. Anaphylaxis causes features such as wheeze, throat swelling, hypotension or collapse and is an emergency. Pregnancy needs obstetric advice if contractions or fetal concerns occur. The decision should be recorded with stage, test titres, pregnancy status, partner support and a written follow-up plan.
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