Sexually Transmitted Infections

Genital infections look like a long list of organisms with similar-sounding syndromes. Two questions collapse most of it.

Is the ulcer painful, and how many are there? Pain and number separate the genital ulcer diseases more reliably than any other bedside feature, and they do it before any test is available.

What else does this patient have? Sexually transmitted infections cluster, because they share a route of acquisition. A patient with one has, by definition, had an exposure that could transmit all the others, which is why the diagnosis of any STI is an indication to test for the rest, including HIV and syphilis.

A third principle runs through management and is often neglected. Treating the patient without treating the partner guarantees reinfection, so partner notification is part of the prescription rather than an optional social intervention.

1. The Genital Ulcer

Two entries deserve emphasis because they are so often reversed.

Syphilitic chancre is painless and indurated with a clean base. The induration is what makes it feel like a button under the finger, and the lack of pain is why patients ignore it and present later in secondary disease.

Chancroid is painful, multiple and ragged with an undermined edge. It suppurates, and its inguinal nodes can rupture through the skin.

Two further points are frequently examined.

The groove sign of lymphogranuloma venereum is a linear depression created by the inguinal ligament separating enlarged nodes above and below it.

Donovanosis produces pseudobuboes, which are subcutaneous granulomas rather than true lymph nodes, and Donovan bodies are seen within macrophages on tissue smear.

Mixed infections are common, so a clinically obvious diagnosis does not exclude a second organism, and syphilis serology and HIV testing are indicated regardless of appearance.

2. Syphilis

Syphilis is a systemic disease with a skin manifestation, and its stages are separated by latency rather than by severity.

Primary syphilis produces the chancre, which heals spontaneously in three to six weeks whether or not it is treated. Spontaneous healing is therefore not evidence of cure and is the reason the disease progresses undetected.

Secondary syphilis appears weeks to months later as a generalised eruption that characteristically involves the palms and soles, with generalised lymphadenopathy, mucous patches, condylomata lata in warm moist areas, and patchy moth-eaten alopecia.

It is the great imitator, and its principal mimic in practice is pityriasis rosea, which lacks palm and sole involvement and begins with a herald patch.

Latent syphilis is seropositivity without symptoms, divided into early latent within the first year and late latent thereafter, a distinction that changes treatment duration.

Tertiary syphilis produces gummata, cardiovascular disease with aortitis and aortic regurgitation from vasa vasorum endarteritis, and neurosyphilis with tabes dorsalis, general paresis and the Argyll Robertson pupil that accommodates but does not react.

Testing

The tests answer different questions and the distinction is examinable.

Non-treponemal tests, VDRL and RPR, measure reagin and are quantitative, so they are used for screening and, importantly, for monitoring response to treatment, since titres fall after successful therapy.

Treponemal tests, TPHA and FTA-ABS, detect antibody to the organism, are more specific, and remain positive for life, so they cannot distinguish current from treated infection.

Biological false positive VDRL occurs in pregnancy, autoimmune disease including antiphospholipid syndrome, and several acute infections, which is why a reactive screening test is confirmed treponemally.

The prozone phenomenon is a false negative VDRL caused by antibody excess in secondary syphilis, resolved by diluting the serum. It is a favourite examination point precisely because the test fails when the disease is most florid.

Treatment

Benzathine penicillin remains first-line and has no resistance, which is remarkable for an organism treated for eighty years. Early syphilis needs a single dose; late latent and tertiary disease need three weekly doses.

Penicillin-allergic pregnant women must be desensitised and given penicillin, because no alternative reliably treats the fetus.

The Jarisch-Herxheimer reaction is fever, chills and worsening rash within hours of the first dose, caused by release of treponemal antigens rather than by allergy. It is self-limiting, must not be mistaken for penicillin allergy, and matters in pregnancy where it can precipitate contractions.

Syphilis in pregnancy and the newborn

Screening every pregnant woman for syphilis is one of the highest-value interventions in antenatal care, because untreated maternal infection causes stillbirth, prematurity, neonatal death and congenital syphilis, and a single injection prevents all of it.

Treponemes cross the placenta at any stage of pregnancy, so the older teaching that transmission occurs only after the fourth month is wrong and should not be relied on.

Early congenital syphilis presents in the first two years with snuffles, a maculopapular rash involving palms and soles, hepatosplenomegaly and osteochondritis producing pseudoparalysis of Parrot.

Late congenital syphilis produces the stigmata that persist: interstitial keratitis, eighth nerve deafness and Hutchinson incisors, which together form the Hutchinson triad, alongside a saddle nose, frontal bossing and sabre tibia.

3. Urethritis and Cervicitis

Gonococcal urethritis produces a copious purulent discharge with a short incubation of two to five days. Gram stain shows intracellular Gram-negative diplococci.

Non-gonococcal urethritis, most often Chlamydia trachomatis, produces a scanty mucoid discharge after a longer incubation.

Both are treated together in practice, because coinfection is common and because chlamydia is frequently asymptomatic.

Gonococcal antimicrobial resistance has escalated steadily through sulphonamides, penicillins, tetracyclines, quinolones and now increasingly cephalosporins, which is why treatment recommendations change and why test of cure matters.

Chlamydia is the more dangerous organism in women despite causing milder symptoms, because asymptomatic infection ascends to produce pelvic inflammatory disease, tubal factor infertility and ectopic pregnancy.

Complications worth carrying include disseminated gonococcal infection with pustular skin lesions, tenosynovitis and arthritis, and reactive arthritis following chlamydial infection with its triad of arthritis, conjunctivitis and urethritis.

4. Discharge, Warts and Infestations

Bacterial vaginosis is not an infection in the usual sense but a shift in flora away from lactobacilli, giving a thin grey discharge with a fishy odour, a positive whiff test, clue cells and a raised pH above 4.5.

Trichomoniasis gives a frothy yellow-green discharge with a strawberry cervix and motile trichomonads on wet mount, and it is the one of the three that is genuinely sexually transmitted and therefore requires partner treatment.

Vulvovaginal candidiasis gives thick white curd-like discharge with intense itch and a normal pH.

Anogenital warts are caused by HPV types 6 and 11, the low-risk types, whereas types 16 and 18 drive cervical and oropharyngeal cancer. HPV vaccination prevents both, which is why it is a cancer vaccine as much as an STI vaccine.

Molluscum contagiosum in the genital area in adults is sexually transmitted, and extensive disease suggests immunosuppression.

Pubic lice and scabies are transmitted by close contact, and scabies in the genital area produces characteristically itchy nodules that persist after mites are eradicated.

5. HIV and the Skin

The skin frequently declares HIV before any test is requested, and several conditions in earlier chapters serve as markers.

Herpes zoster in a young adult, extensive facial molluscum contagiosum in an adult, severe or abruptly worsening seborrhoeic dermatitis, oral candidiasis without an obvious cause, and crusted scabies all suggest impaired cell-mediated immunity.

Kaposi sarcoma, driven by human herpesvirus 8, produces violaceous plaques and nodules and is an AIDS-defining illness.

Oral hairy leukoplakia is an Epstein-Barr virus-driven white plaque on the lateral tongue that, unlike candidiasis, cannot be scraped off.

Any STI increases HIV transmission risk in both directions, because ulceration breaches the barrier and inflammation recruits the very CD4 cells the virus infects. This is the biological reason STI control is an HIV prevention strategy.

Prevention

Condoms, treatment as prevention with viral suppression rendering HIV untransmittable, and pre-exposure prophylaxis are established.

Doxycycline post-exposure prophylaxis is the newer intervention. A 200 mg dose taken within 24 hours and no later than 72 hours after condomless sex substantially reduces bacterial STIs, with the largest effects on chlamydia and syphilis and much less on gonorrhoea.

It is not a general recommendation. Current guidance targets specific higher-incidence populations rather than the general population, and there is a genuine and documented concern that widespread use selects for doxycycline resistance, which has already been observed in gonorrhoea following implementation.

6. Genital Herpes and Its Particular Problems

Herpes simplex deserves separating from the other ulcer diseases because it is chronic, recurrent and carries a disproportionate psychological burden.

Primary infection is the most severe episode, with multiple painful grouped vesicles that ulcerate, tender bilateral inguinal nodes, fever and malaise, and sometimes urinary retention from sacral radiculitis.

Recurrences are milder, shorter, unilateral and often preceded by a prodrome of tingling, because the virus reactivates from a single sacral ganglion rather than seeding the whole area afresh.

HSV-1 is now a common cause of genital herpes, particularly in first episodes among younger people, and it recurs less frequently than HSV-2, which changes the counselling considerably.

Three clinical points carry the marks.

Asymptomatic viral shedding transmits infection, so the absence of visible lesions does not mean the absence of risk, and this is what makes the infection so difficult to contain.

Suppressive antiviral therapy reduces both recurrences and transmission to a partner, which makes it an intervention for the couple rather than only for the patient.

Herpes in late pregnancy is the dangerous scenario. A primary episode near delivery carries the highest risk of neonatal herpes, because the mother has not yet developed protective antibody to transfer, and caesarean section is considered where lesions are present at labour.

Neonatal herpes may present as localised skin, eye and mouth disease, as central nervous system disease, or as disseminated infection, and the disseminated form carries a high mortality.

7. The Syndromic Approach

India and many other settings use syndromic management, in which treatment is directed at a syndrome rather than waiting for an organism.

The reasoning is pragmatic rather than ideal. Laboratory confirmation is often unavailable or delayed, patients frequently do not return, and untreated infection continues to transmit and to damage.

The syndromes are genital ulcer disease, urethral discharge, vaginal discharge, lower abdominal pain, inguinal bubo and scrotal swelling, each with a colour-coded treatment kit in the national programme.

Its weakness is worth stating honestly. Syndromic management overtreats, particularly in women where vaginal discharge is a poor predictor of cervical infection, and it contributes to antimicrobial pressure. It is a compromise justified by access rather than a scientific ideal.

Four things must accompany every syndromic treatment: partner notification and treatment, condom counselling, HIV and syphilis testing, and a follow-up appointment.

8. Worked Examples

Example 1. A 26-year-old man has a single painless indurated genital ulcer with a clean base and bilateral rubbery non-tender inguinal nodes. He wants only a cream. What do you do?

This is a primary syphilitic chancre, identified by the combination of a single painless indurated ulcer with a clean base and non-tender rubbery bilateral nodes. Painless and indurated is the pairing that matters.

Confirm with dark-ground microscopy where available and with serology, remembering that non-treponemal tests may still be negative in very early primary disease so repeat testing is needed.

Treat with a single dose of benzathine penicillin. Test for HIV and other sexually transmitted infections, because coinfection is common and any STI diagnosis is an indication to look for the rest. Notify and treat partners. Warn him that the ulcer would have healed by itself without treatment, which is precisely why untreated syphilis progresses silently.

Example 2. A patient with secondary syphilis has a VDRL reported as non-reactive. The clinical picture is convincing. What has happened and what do you do?

The prozone phenomenon. In secondary syphilis antibody titres are extremely high, and excess antibody prevents the lattice formation that the flocculation test depends on, so the undiluted serum gives a falsely non-reactive result.

The remedy is to request the test on diluted serum, which restores the antigen-antibody ratio and reveals a strongly reactive result at higher dilutions. A treponemal test such as TPHA will also be positive.

The general lesson is that this test fails precisely when the disease is most florid, which is the opposite of intuition, and a non-reactive VDRL in a patient with a palm and sole rash and generalised lymphadenopathy should never be accepted at face value.

Example 3. A pregnant woman with latent syphilis reports a penicillin allergy. What is the correct management?

Desensitisation followed by penicillin. Benzathine penicillin is the only agent reliably shown to treat the fetus as well as the mother, and alternatives such as doxycycline are contraindicated in pregnancy while erythromycin does not cross the placenta adequately to treat congenital infection.

The allergy history should first be examined carefully, since many reported penicillin allergies are not genuine IgE-mediated reactions. If genuine, formal desensitisation is performed in a setting equipped to manage anaphylaxis, and penicillin is then given.

She should be warned about the Jarisch-Herxheimer reaction, which occurs within hours of the first dose from released treponemal antigens, is not an allergic reaction, and in pregnancy can provoke uterine contractions and fetal distress, so treatment is given where fetal monitoring is available.

Example 4. A 30-year-old woman has been treated syndromically for vaginal discharge three times in six months. Discuss what is going wrong.

Repeated syndromic treatment without resolution indicates that at least one of four supporting steps has been omitted, and the most likely is partner treatment. Reinfection from an untreated partner is the commonest reason for apparent treatment failure, and treating the patient alone guarantees recurrence.

The second possibility is that the syndrome is being mistreated. Vaginal discharge is a poor predictor of cervical infection, and the actual cause may be bacterial vaginosis, which is a flora shift rather than a sexually transmitted infection, or candidiasis, neither of which responds to antibacterial cover aimed at gonorrhoea and chlamydia.

Third, recurrent candidiasis specifically should prompt testing for diabetes and HIV. Fourth, she needs HIV and syphilis serology, which should have accompanied the first episode.

The practical answer is to move beyond syndromic management in a patient with recurrent disease, obtaining microscopy, pH and specific testing, and to treat the partner.

Example 5. A young man asks for doxycycline to take after sexual exposures because a friend told him it prevents infections. How do you respond?

He is describing doxycycline post-exposure prophylaxis, which is a real intervention with genuine evidence. A 200 mg dose within 24 hours and no later than 72 hours after condomless sex substantially reduces bacterial sexually transmitted infections, with the strongest effect on chlamydia and syphilis.

Three qualifications matter. The effect on gonorrhoea is much weaker, so it does not cover the full range. Current guidance recommends it for specific higher-incidence populations, particularly men who have sex with men and transgender women with a bacterial STI in the past year, rather than for the general population. And there is documented concern that widespread use selects for resistance, with reduced doxycycline effectiveness against gonorrhoea already observed after implementation in some settings.

The right response is therefore neither refusal nor a prescription on request, but a risk assessment, discussion of condoms and pre-exposure prophylaxis for HIV where relevant, testing for existing infection, and a considered decision about whether he falls within the target group.

Summary

Pain and number separate genital ulcers before any test is available.

Syphilitic chancre is single, painless and indurated with a clean base.

Chancroid is multiple, painful and ragged with undermined edges and suppurative nodes.

The groove sign belongs to lymphogranuloma venereum; pseudobuboes belong to donovanosis.

Mixed infection is common, so appearance does not exclude a second organism.

The chancre heals spontaneously, which is why untreated syphilis progresses silently.

Secondary syphilis involves the palms and soles; pityriasis rosea does not.

Non-treponemal tests are quantitative and monitor treatment; treponemal tests stay positive for life.

The prozone phenomenon causes a false negative VDRL in florid secondary syphilis.

Benzathine penicillin remains first-line with no documented resistance.

Penicillin-allergic pregnant women are desensitised, because no alternative treats the fetus.

The Jarisch-Herxheimer reaction is antigen release, not allergy.

Gonorrhoea gives copious purulent discharge quickly; chlamydia gives scanty mucoid discharge later.

Chlamydia causes more harm in women because it is asymptomatic and ascends.

Bacterial vaginosis is a flora shift with clue cells and pH above 4.5.

Trichomoniasis is the discharge syndrome that requires partner treatment.

HPV 6 and 11 cause warts; 16 and 18 cause cancer, and vaccination prevents both.

Several skin conditions are markers of undiagnosed HIV.

Any STI raises HIV transmission risk in both directions.

Doxycycline prophylaxis works best for chlamydia and syphilis but risks selecting resistance.

Syndromic management trades precision for access, and requires partner treatment, counselling, testing and follow-up.