Penile cancer is rare but is often diagnosed late, frequently because of attribution to benign conditions (balanitis, lichen sclerosus) without biopsy. Lichen sclerosus is an important risk factor — male genital LS is associated with penile intraepithelial neoplasia and penile cancer, although the reported risk varies considerably between studies. Any persistent erosion, ulcer, induration, lump or changing lesion in known lichen sclerosus requires urgent specialist assessment and possible biopsy. HPV infection (especially types 16 and 18) is causally implicated in a substantial proportion of penile SCCs — making HPV vaccination of adolescent males (now part of the NHS schedule) a penile cancer prevention strategy. Paraphimosis is a urological emergency that is frequently encountered in primary care — it can occur after a medical examination (failure to replace foreskin after catheterisation or examination), after sexual activity, or spontaneously in men with phimosis. The mechanism is that the tight retracted prepuce acts as a tourniquet, obstructing venous and lymphatic drainage → oedema → arterial obstruction → gangrene. The glans becomes progressively more engorged and cyanotic. Manual reduction (gentle compression and lubrication) is an emergency procedure for a trained clinician; escalate promptly to A&E/urology if it is not quickly successful. Dorsal slit is a specialist procedure.

The sexual history is the most important and most frequently incomplete part of the penile irritation consultation — many GPs find it uncomfortable to ask or assume the diagnosis is non-sexual based on age or relationship status. This is a well-documented cause of delayed STI diagnosis. BASHH guidelines and RCGP SCA competencies both emphasise that any genital complaint in a person of any age or relationship status warrants an STI risk assessment. The BASHH recommended approach is the "5 Ps": Partners (number, gender), Practices (oral, anal, vaginal), Protection (condom use), Past STI history, and Pregnancy plans. Asking this systematically rather than ad hoc is both more comfortable for the clinician and more acceptable to the patient. Diabetes-associated recurrent candidal balanitis is one of the most important presentations to recognise — recurrent, severe or resistant candidal balanitis in a man, especially if obese, middle-aged, or with other risk factors, should prompt an HbA1c. Undiagnosed type 2 diabetes frequently presents first as recurrent candidal balanitis — glycosuria provides a nutrient-rich environment for Candida albicans on the glans and prepuce.

Syphilis is one of the most important diagnoses not to miss in penile ulceration — the primary chancre is classically painless and indurated, and is frequently located under the foreskin where it is invisible without retraction. Patients do not present with "a sore" because it does not hurt. They may present weeks later with secondary syphilis features (widespread rash, condylomata lata, constitutional symptoms) without ever having noticed the primary ulcer. Syphilis diagnoses in England are at their highest level since 1948 (UKHSA, 2024). Any genital ulcer, even if painless, must have syphilis serology alongside an STI screen. The painlessness of the chancre is the key teaching point — painful penile ulcers suggest herpes; painless indurated ulcers suggest syphilis; painful non-indurated ulcers in tropical settings suggest chancroid (Haemophilus ducreyi). Lichen sclerosus of the penis (BXO) deserves the same clinical attention as vulval lichen sclerosus — its association with penile intraepithelial neoplasia and penile cancer means ongoing self-examination and urgent specialist assessment, with possible biopsy, of any persistent erosion, ulcer, induration, lump or changing lesion. Many GPs are more familiar with vulval LS but the penile condition is equally important and equally undertreated. A very potent topical steroid (clobetasol propionate 0.05%) is first-line, using a specialist-directed regimen individualised to the patient — the vulval tapering schedule is largely extrapolated and is not a universal male protocol.

Inspecting the glans and inner prepuce, where safe and possible, matters — an unexamined glans can delay penile cancer diagnosis — but a scarred or painful foreskin should never be forcibly retracted. The inner prepuce and glans are the two most common sites for penile SCC. Non-retractile foreskin (phimosis) is both a risk factor for penile cancer (HPV trapping, chronic inflammation) and a physical barrier to examination. When the foreskin cannot be retracted for examination and there are persistent symptoms or a suspicious lesion, urgent urology assessment is warranted — both to enable examination and to assess phimosis for treatment. Gonorrhoea culture (in addition to NAAT) is essential whenever gonorrhoea is suspected or when NAAT is positive — culture allows antimicrobial sensitivity testing, which is critical given the dramatic rise in antimicrobial resistance in Neisseria gonorrhoeae. Ceftriaxone-resistant gonorrhoea has been identified in England, several cases linked to travel. BASHH therefore advises obtaining culture wherever possible before treatment, particularly if discharge is present. A NAAT-positive result without culture means treatment is given empirically (ceftriaxone 1 g IM) but resistance data are not available for that specific isolate — culture is the safety net.

A short course of a topical corticosteroid to the phimotic ring may be considered in selected adults with non-urgent pathological phimosis, using the exact preparation and regimen specified by the local urology pathway — it can avoid the need for circumcision in some patients. The mechanism is steroid-induced softening of the fibrotic phimotic ring through suppression of the local inflammatory response and promotion of collagen remodelling. This should be tried before circumcision is offered for phimosis without lichen sclerosus. If lichen sclerosus is the cause of phimosis (BXO), a very potent steroid (clobetasol propionate 0.05%) is used instead, under a specialist-directed plan. GUM clinic referral for all confirmed STIs is the standard of care — GUM clinics provide: partner notification services (index case is notified of all contacts being tested without naming the index patient), contact tracing infrastructure, free STI testing for contacts, PrEP (HIV pre-exposure prophylaxis for people at substantial HIV risk), PEP (post-exposure prophylaxis), psychosexual support, and surveillance data for public health. Gonorrhoea, syphilis, herpes and urethritis management should be sexual-health-led, and partner notification is a specialist sexual-health function.

The switch from azithromycin to doxycycline as first-line for chlamydia reflects important resistance data — the 2018 BASHH guideline change was driven by evidence that azithromycin 1 g single dose has higher treatment failure rates for rectal and pharyngeal chlamydia infection, and that single-dose treatment selects for macrolide resistance in Mycoplasma genitalium (a co-pathogen causing NGU that responds poorly to azithromycin after a single-dose exposure). Doxycycline 100 mg BD × 7 days is highly effective for urogenital, rectal and pharyngeal chlamydia. The GUM referral after chlamydia diagnosis is essential for partner notification — partner notification and look-back periods follow the current BASHH infection-specific guidance and are coordinated by sexual-health clinicians — the infrastructure of GUM clinics (trained health advisers, contact slips, anonymous notification) is more effective. Rising ceftriaxone resistance in gonorrhoea is an emerging global concern — BASHH increased the recommended ceftriaxone dose from 500 mg to 1 g in its 2019 guideline in response to rising resistance, and the 2025 guideline keeps 1 g as sole first-line therapy. Obtaining culture wherever possible before treatment ensures resistance data are captured for public health surveillance and individual treatment modification if culture-directed therapy is needed.

The fixed drug eruption is clinically important because it is frequently misdiagnosed as herpes, balanitis, or contact dermatitis — particularly when it presents on the glans penis as a painful, erythematous, or ulcerated lesion. The distinguishing feature is recurrence at exactly the same site with each drug exposure — the lesion "heals" leaving a post-inflammatory hyperpigmented macule, then re-activates to a blistering erosive lesion the next time the drug is taken. Co-trimoxazole (trimethoprim-sulfamethoxazole) is the most common cause on the glans. The reaction is T-cell mediated — there is residual memory T-cell infiltration at the site of the previous reaction, which is activated by systemic drug exposure. Definitive diagnosis requires identifying and documenting the implicated drug and its temporal relationship with the lesion. The Jarisch-Herxheimer reaction in syphilis treatment is caused by massive cytokine release (TNF-α, IL-6, IL-8) from the rapid lysis of Treponema pallidum spirochaetes by penicillin. It is common in early syphilis, typically 2–8 hours after the first penicillin dose. It is self-limiting but can be alarming — patients must be pre-warned, given paracetamol at the time of injection, and advised to rest and remain well hydrated for 24 hours. It is not an allergic reaction to penicillin.

SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin) cause glycosuria as their mechanism of action — and glycosuria directly increases the risk of genital mycotic infections (candidal balanitis in men, vulvovaginal candidiasis in women) by providing a nutrient-rich, acidic environment on the genital skin. GPs should specifically counsel diabetic men starting SGLT2 inhibitors about this risk and advise vigilant penile hygiene. If recurrent genital candidiasis occurs on an SGLT2 inhibitor, assess glycaemic control, hygiene, phimosis and alternative causes, and discuss the balance of genital-infection burden against the cardiovascular/renal benefits with the diabetes prescriber — do not switch automatically to metformin. The U=U (Undetectable = Untransmittable) principle is now scientifically established by the PARTNER, PARTNER2, and Opposites Attract studies — these demonstrated no within-couple HIV transmissions during condomless sex when the HIV-positive partner had an undetectable viral load on effective ART. Communicating U=U to patients with HIV in primary care reduces stigma, improves treatment adherence, and reduces transmission anxiety.

Persistence despite appropriate treatment is the most important safety-netting trigger for this presentation — any persistent, changing or treatment-resistant lesion needs urgent specialist assessment, with biopsy by a clinician experienced in penile dermatoses and cancer, regardless of how benign it appears clinically. This is because penile SCC can mimic all of the benign conditions in this pathway: it can appear as a "chronic balanitis" (red granular plaque), a "chronic lichen sclerosus" lesion (white plaque), a "persistent wart" (papillomatous lesion), or an "ulcer from herpes" (shallow erosion). The biopsy is the only way to definitively exclude malignancy. For patients with lichen sclerosus, the threshold is even lower — any new area of induration, any ulcer, or any nodule in a patient with known LS should trigger urgent urology review within days, not weeks. The RPR (Rapid Plasma Reagin) titre monitoring after syphilis treatment is the serological test of cure — it is a quantitative test that measures the amount of non-treponemal antibody. A 4-fold fall (e.g., from 1:32 to 1:8) by 3 months indicates successful treatment response. Failure to achieve this fall raises concern for treatment failure or re-infection, requiring retreatment. GPs who have treated or are co-managing syphilis should ensure this follow-up serology is arranged and reviewed at each time point.