🤕 Anogenital Ulcers — Assessment & Management

Primary syphilis is the most important single STI diagnosis not to miss in primary care — infectious syphilis diagnoses in England reached 9,513 in 2023 (UKHSA), the highest annual number since 1948, making it one of the fastest-rising STIs. The primary chancre is pathognomonic but frequently missed because: (1) it is painless (unlike HSV which is intensely painful), so patients may not notice it; (2) it can occur on the cervix, vagina, or rectum where it is not visible; (3) it resolves spontaneously in 3-6 weeks even without treatment, leaving the patient in the latent phase; and (4) it can be confused with other genital ulcers. The GP assessment standard: any painless, hard-based, well-defined genital ulcer in a sexually active adult, in any anatomical location, is syphilis until syphilis serology proves otherwise. Send laboratory syphilis serology with a treponemal screening assay and quantitative RPR; the laboratory performs confirmatory testing according to its validated algorithm (exact assays are laboratory-dependent). Treponemal tests usually remain positive for life and are not suitable for monitoring treatment response. A negative serology does not exclude very early primary syphilis — repeat testing (about 2 weeks after a negative lesion test, BASHH) if suspicion remains. Treatment and partner notification via GUM.

The Lipschutz ulcer (ulcus vulvae acutum) is an important diagnosis of exclusion that avoids an incorrect STI label and patient distress — it presents as an acute painful vulvar ulcer, often in a girl or young woman, and can occur in sexually active people too. It may follow EBV, CMV, influenza, COVID-19 or other systemic infection. The clinical features: acute onset, intensely painful ulcers on the labia majora or labia minora, often multiple, shallow with grey or necrotic base, occurring within days of a viral prodrome. It is a diagnosis of exclusion — appropriate STI testing (including HSV PCR) is still needed. Paul-Bunnell testing is not required; use targeted EBV/CMV serology only when clinically indicated. Management: supportive (topical lidocaine gel, oral analgesia, saline bathing), with specialist advice for severe disease. Recognising it avoids an incorrect STI diagnosis and its psychological impact.

The 4th generation HIV test (combined antigen-antibody test) is the current standard for HIV diagnosis in the UK — it detects both HIV antibodies and HIV p24 antigen (detectable before antibodies develop). This significantly reduces the window period compared to 3rd generation antibody-only tests. BHIVA/BASHH/BIA guidance uses a 45-day window period for fourth-generation laboratory testing (point-of-care antibody tests have a longer window): a negative result does not exclude infection until at least 45 days after exposure, so repeat testing is required if exposure was more recent or acute HIV is clinically suspected. Consider HIV RNA/specialist testing in suspected acute seroconversion with negative or indeterminate serology. If there was a high-risk exposure within 72 hours, do not delay PEP assessment — refer urgently to sexual health, A&E or HIV services.

LGV (Lymphogranuloma venereum) anorectal syndrome in MSM is one of the most clinically significant STI syndromes to recognise in primary care — the anorectal presentation (proctitis) causes rectal pain, tenesmus, bloody or mucoid anal discharge, and constipation, and is frequently misdiagnosed as inflammatory bowel disease (particularly Crohn's proctitis) because the endoscopic appearance (rectal erythema, ulceration, friability) is similar. The key clinical discriminator: LGV proctitis occurs in MSM who practise receptive anal sex and may have concurrent STIs; IBD typically occurs in a different demographic and does not have concurrent STIs. Any MSM presenting with proctitis should have rectal NAAT swab for chlamydia + LGV genotyping + other STI screens before colorectal or gastroenterological investigation. Treatment is via GUM, which uses a longer doxycycline course than for standard chlamydia.

The primary care HIV test offer in any patient presenting with an STI or anogenital ulcer is recommended in the BHIVA/BASHH/BIA adult HIV testing guidelines (2020) and NICE NG60 (2016) — HIV testing should be offered at every STI consultation as a routine, not a targeted, investigation. The rationale: HIV-positive individuals who are unaware of their status are the primary drivers of new HIV transmissions; HIV testing at all STI contacts maximises case detection; modern HIV treatment (ART) is highly effective and starts immediately after diagnosis. The GP should frame the HIV test as routine: 'We routinely test for HIV as part of our sexual health check — it is a simple blood test and I recommend it for everyone being assessed for any STI.' The opt-out approach (testing unless declined) significantly increases HIV testing rates compared to the opt-in approach.

The Jarisch-Herxheimer reaction after syphilis treatment is an important patient safety counselling point — many patients with primary or secondary syphilis develop the reaction, usually within 24 hours of their first treatment: fever, rigors, headache, myalgia, and worsening of existing lesions. It is caused by the rapid release of lipoproteins from dying Treponema pallidum spirochaetes, triggering a systemic inflammatory response. The reaction is expected, transient, and is not an allergic reaction or treatment failure — manage symptomatically. In pregnancy it may precipitate uterine contractions or fetal compromise, so obstetric advice is needed. Patients must be warned before treatment: 'You may feel quite unwell with fever and chills tonight — this is the infection dying off and it means the treatment is working. Take paracetamol, rest, and drink fluids. Contact us or NHS 111 the same day if you feel very unwell or it lasts beyond 24 hours; call 999 if you have difficulty breathing or swelling of your face or lips. If you are pregnant, contact your maternity unit the same day for contractions or reduced baby movements.' Failing to warn the patient often leads to unnecessary re-presentation to A&E with the self-described 'allergic reaction' to penicillin.

The doxycycline 21-day course for LGV proctitis is a critical prescribing distinction from standard chlamydia treatment — Chlamydia trachomatis serotypes D-K (non-LGV) are treated first-line with doxycycline 100 mg BD x 7 days (BASHH chlamydia guideline 2026); azithromycin (1 g then 500 mg daily for 2 days) is reserved for pregnancy, breastfeeding or selected doxycycline-intolerant patients per specialist guidance. LGV serovars L1-L3 require a longer doxycycline course managed by GUM (BASHH LGV guidance). A patient treated for 'chlamydia' with azithromycin who actually has LGV will fail treatment, with ongoing proctitis and risk of rectal stricture formation from untreated LGV proctitis. The clinical lesson: any patient with chlamydia confirmed on rectal swab who has symptoms of proctitis (rectal pain, tenesmus, rectal discharge) must have LGV serogrouping requested before selecting antibiotic treatment.

The psychological impact of genital herpes diagnosis is substantial and well-documented — many patients with newly diagnosed genital herpes experience significant anxiety, shame, and relationship distress. The prognosis, however, is usually better than patients initially fear: some people never have a recognised recurrence; most who do have recurrences find they become less frequent and less severe over time; and suppressive therapy reduces recurrences, although response varies. The GP's communication at the time of HSV diagnosis is critical for long-term psychological outcomes — stating clearly: 'Genital herpes is a very common condition. It is manageable, it does not define your sexual health, and there are effective treatments to reduce outbreaks.' This evidence-based reassurance, combined with written information and referral to specialist sexual health nursing, significantly reduces anxiety and stigma.

The neonatal herpes transmission risk from a mother with genital HSV is one of the most important antenatal safety discussions in primary care — neonatal HSV carries a high mortality without treatment and causes devastating neurological sequelae in survivors. The highest-risk scenario: primary genital HSV infection in the third trimester (particularly at ≥36 weeks) because: (1) the mother has not yet developed protective antibodies; (2) viral shedding is maximal; and (3) the infant will not receive passive antibody protection. Management: primary or non-primary first-episode genital herpes in the third trimester needs same-day obstetric contact and obstetric/GUM management — planned Caesarean section is generally recommended, especially within 6 weeks of delivery, because the risk of neonatal transmission during vaginal delivery is high. Recurrent HSV alone does not routinely require planned Caesarean. Suppressive aciclovir from 32 weeks (earlier where preterm delivery risk is high) reduces viral shedding and recurrence at delivery (BASHH/RCOG 2024). All women with a history of genital HSV should inform their midwife and obstetrician at booking.