Synopsis
Approach genital ulcers without relying on appearance alone, exclude urgent herpes and syphilis, recognise LGV, chancroid, donovanosis and mpox, and investigate non-infective disease.
- Most genital ulcers in UK practice are herpes or syphilis, and coinfection means both are tested regardless of appearance.
- Swab fresh lesions for HSV NAAT and obtain syphilis serology with repeat testing after the early window when required.
- Ask exact travel, country of partner, oral and anal exposure, sex-work contact, skin-to-skin networks, systemic symptoms and medicines.
- LGV commonly presents as severe proctitis after rectal exposure or with transient ulcer followed by painful nodes; treat with doxycycline for 21 days.
- Chancroid causes painful ragged ulcers with tender suppurative nodes and is mainly imported; confirm through specialist microbiology where possible.
- Donovanosis causes slowly progressive painless beefy-red friable ulcers that bleed easily after exposure in endemic regions.
- Mpox lesions are deep, firm and often umbilicated, with systemic symptoms and lymphadenopathy; follow current UKHSA testing and isolation advice.
- Biopsy persistent or atypical ulcers to assess malignancy, inflammatory disease, fixed-drug eruption and other non-infective causes.
Key red flags
Rapidly spreading genital pain, swelling, crepitus or skin necrosis suggests Fournier gangrene and needs emergency debridement.
Severe rectal pain, bleeding, tenesmus, fever or constipation after anal exposure suggests LGV proctitis or another invasive rectal infection.
Firm umbilicated lesions with fever, lymphadenopathy and epidemiological exposure may represent mpox and require infection-control action.
A persistent indurated, fungating or bleeding ulcer requires cancer assessment and biopsy even when an STI test is positive.
Recurrent oral and genital ulcers with eye pain, neurological or vascular symptoms suggests Behçet disease.
Ulceration in pregnancy, profound immunosuppression or a neonate needs immediate specialist evaluation.
Severe anorectal pain, discharge, bleeding, tenesmus and systemic symptoms after rectal exposure resembles inflammatory bowel disease.
Deep firm lesions evolving synchronously through papule, vesicle and pustule stages with lymphadenopathy and systemic symptoms suggest mpox.
Investigation priorities
Identify the most common infectious cause using a swab from a fresh vesicle or ulcer base.
Management branches
A new anogenital ulcer is identified and no single cause has been confirmed.
- Take HSV NAAT, syphilis serology and direct treponemal testing where available before lesion treatment.
- Offer HIV and exposure-site chlamydia and gonorrhoea tests and take a pregnancy test where relevant.
- Start early herpes or syphilis treatment when clinical probability and follow-up risk justify it rather than waiting for every result.
- Provide pain, urinary and wound support and advise abstinence until diagnosis, treatment and partner plan are clear.