Penile cancer is rare (approximately 700 new cases per year in the UK) but has a well-documented problem of delayed diagnosis — the average delay from first GP presentation to diagnosis is 6–12 months, predominantly due to attribution to benign conditions (balanitis, lichen sclerosus) without biopsy. The most important risk factor is lichen sclerosus — men with LS have a 5% lifetime risk of penile SCC (equivalent to the well-known vulval SCC risk in women with LS). Any non-healing penile lesion in a patient with known lichen sclerosus must be biopsied urgently. HPV infection (types 16 and 18) is causally implicated in 50% 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 with ice compression and lubrication (generous lubricant over glans, compress firmly between both thumbs, push glans through prepuce ring) can be attempted but should be escalated to A&E if not successful within 10–15 minutes.

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 candida (more than 2 episodes per year) in a man, especially if obese, middle-aged, or with other risk factors, should prompt urgent 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. UK syphilis rates have increased by over 700% since 2012 — it is now at a 50-year high. 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 — the 5% lifetime SCC risk requires annual review with inspection and a low threshold for biopsy of any new lump, ulcer, or area of induration. Many GPs are more familiar with vulval LS but the penile condition is equally important and equally undertreated. Potent topical steroid (clobetasol propionate 0.05%) applied with the same tapering protocol as for vulval LS is the evidence-based first-line treatment.

The instruction to fully retract the foreskin before examining the penis cannot be overstated — an RCE (Royal College of Surgeons) audit of delayed penile cancer diagnosis found that in 40% of cases where penile cancer was initially missed, the GP had not examined under the foreskin. 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, urology referral 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 (ESBL-producing strains) has been identified in multiple UK outbreaks. BASHH guidelines therefore require culture before treatment for all confirmed gonorrhoea. 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.

The topical steroid trial for phimosis (betamethasone 0.05% cream applied to the phimotic ring BD × 6 weeks with gentle stretching) is the evidence-based first-line treatment for physiological or pathological phimosis in boys and adults — it achieves full or partial retraction in 70–80% of cases, avoiding the need for circumcision. 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), clobetasol propionate 0.05% is used instead (same potency but higher concentration — better penetration through the thickened sclerotic tissue). 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), PEP (post-exposure prophylaxis), psychosexual support, and surveillance data for public health. GPs can initiate STI treatment but should always refer to GUM for full partner notification, especially for gonorrhoea and syphilis where contact tracing is critical.

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 (up to 22% failure rate in some studies), 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 achieves >97% cure rates for urogenital, rectal, and pharyngeal chlamydia. The GUM referral after chlamydia diagnosis is essential for partner notification — BASHH partner notification standards require all sexual contacts within 3 months to be tested and treated. GPs can provide this service but 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 2022 specifically in response to UK cases of treatment failure with 500 mg. Culture before treatment is mandatory to ensure 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 occurs in 50–70% of patients with primary 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. The incidence of genital mycotic infections with SGLT2 inhibitors is approximately 3–8% in men (vs 0.5% with placebo). GPs should specifically counsel diabetic men starting SGLT2 inhibitors about this risk and advise vigilant penile hygiene. If recurrent fungal balanitis occurs on an SGLT2 inhibitor, a medication switch review with the diabetes team is warranted — although the cardiovascular and renal benefits of SGLT2 inhibitors often outweigh the infection side effect and topical antifungal prophylaxis (clotrimazole 1% cream 2–3× per week) can be used alongside. The U=U (Undetectable = Untransmittable) principle is now scientifically established by the PARTNER, PARTNER2, and Opposites Attract studies — these collectively involved over 75,000 condomless sex acts and demonstrated zero HIV transmissions 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.

The 4-week non-healing rule for penile lesions is the most important safety-netting instruction for this presentation — any lesion that has not healed after 4 weeks of appropriate treatment for the presumed diagnosis must be referred for biopsy via 2WW urology, 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.