Infectious DiseasesTier 2Disease (DEADMAN)

Genito-urinary conditions - anogenital ulcers

Description

Anogenital ulceration in the STI context most commonly reflects HSV (painful, vesicular preceding) or syphilis (painless chancre) - see for the full approach-style differential, history, examination, and management of this presentation

Epidemiology

A common sexual health presentation, with regional variation in relative frequency of causes (HSV and syphilis dominate in most high-income settings; chancroid and LGV are less common but relevant in specific epidemiological contexts/travel history)

Aetiopathogenesis

HSV causes epithelial cell lysis and vesicle formation via direct viral cytopathic effect; syphilis's chancre reflects local Treponema pallidum invasion with a vigorous but initially painless local immune response - the painless nature of the primary chancre is a key, frequently missed diagnostic feature

Diagnosis

HSV PCR and syphilis serology/dark-field microscopy are the key initial tests, guided by lesion characteristics (painful vesicular vs painless indurated ulcer) and risk history
Full STI screen and HIV testing should accompany any anogenital ulcer assessment given the elevated HIV transmission/acquisition risk associated with genital ulceration

Management

Aciclovir/valaciclovir for confirmed or clinically likely HSV; benzathine penicillin for confirmed syphilis (stage-dependent dosing)
Partner notification and contact tracing apply to both, with syphilis being a notifiable disease requiring public health reporting

Associations

HIV co-infection risk (bidirectionally elevated with genital ulceration), painless chancre easily missed/dismissed, HSV asymptomatic shedding and transmission

Natural history & complications

A painless genital ulcer should not be assumed benign - painless is the classic and easily under-recognised presentation of a primary syphilitic chancre, which requires urgent treatment and partner notification despite its unimpressive appearance

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