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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
Key points
- Pathogenesis: excess sebum + follicular hyperkeratinisation + Cutibacterium acnes + inflammation
- First-line: topical adapalene + benzoyl peroxide (Epiduo) or tretinoin + clindamycin
- Oral antibiotics (lymecycline 408 mg OD or doxycycline 100 mg OD) ALWAYS with topical, max 3 months initial
- NEVER prescribe oral antibiotic monotherapy — always combine with topical
- Isotretinoin for severe/scarring acne via specialist — pregnancy prevention programme mandatory
Overview
Acne vulgaris is a chronic inflammatory condition of the pilosebaceous unit involving four key factors: androgen-driven sebum excess, abnormal follicular keratinisation, Cutibacterium acnes proliferation, and inflammation. Lesions range from comedones to papules, pustules, nodules, and cysts. Scarring can result from both disease and manipulation.
Epidemiology
Affects up to 80-90% of adolescents. Peak 14-17 years (females) and 16-19 years (males). Adult female acne increasingly recognised. ~3.5 million GP consultations/year in the UK. Risk factors include family history, hormonal factors (PCOS, puberty), and certain drugs (corticosteroids, lithium, anabolic steroids).
Clinical Features
Symptoms
Open comedones (blackheads) and closed comedones (whiteheads)
Inflammatory papules and pustules on face, back, chest
Pain and tenderness with nodular/cystic lesions
Post-inflammatory hyperpigmentation
Significant psychological distress or suicidal ideation
Sudden onset severe acne with systemic symptoms (acne fulminans)
Signs
Comedones: the hallmark of acne — open (blackheads) and closed (whiteheads)
Inflammatory papules and pustules on face, chest, upper back
Nodules and cysts in severe disease
Scarring: atrophic (ice-pick, boxcar, rolling) or hypertrophic/keloid
Signs of hyperandrogenism: hirsutism, androgenic alopecia (consider PCOS)
Investigations
First-line
Clinical diagnosisNo routine investigations needed
Second-line
Hormonal profileTestosterone, SHBG, DHEA-S, LH/FSH if hyperandrogenism suspected
Specialist
Pregnancy testMandatory before and monthly during isotretinoin
Baseline bloods before isotretinoinFBC, LFT, fasting lipids — monitor monthly
1
General advice
- Non-alkaline syndet cleanser BD
- Avoid picking lesions
- Allow 8-12 weeks for treatment response
2
First-line topical (12-week course)
- Adapalene 0.1% + benzoyl peroxide 2.5% (Epiduo) OD at night
- OR tretinoin 0.025% + clindamycin 1% (Treclin)
- Mild-moderate: benzoyl peroxide 5% + clindamycin 1% (Duac) max 12 weeks
3
Moderate-severe: add oral antibiotic
- Lymecycline 408 mg OD OR doxycycline 100 mg OD
- ALWAYS combine with topical — NEVER monotherapy
- Initial 3 months; max 6 months
4
Specialist: isotretinoin
- 0.5-1 mg/kg/day for 16-24 weeks (cumulative ~120-150 mg/kg)
- MANDATORY pregnancy prevention programme — two forms of contraception
- Side effects: dry lips/skin, myalgia, raised lipids/LFTs, mood changes
5
Women: hormonal therapy
- COCP (especially co-cyprindiol/Dianette for severe acne)
- Dianette: switch to standard COCP after 3-4 months (higher VTE risk)
Complications
- Scarring: Atrophic or hypertrophic — early treatment reduces risk
- Post-inflammatory hyperpigmentation: Common in darker skin
- Psychological impact: Depression, anxiety, suicidal ideation
- Acne fulminans: Rare explosive onset with systemic symptoms — urgent referral
UKMLA Exam Tips
- 1Comedones = acne. No comedones = consider rosacea
- 2NEVER prescribe oral antibiotic monotherapy — always combine with topical
- 3Isotretinoin is teratogenic — pregnancy prevention programme mandatory
- 4Lymecycline/doxycycline are tetracyclines — CI in pregnancy and children <12
- 5Acne + hirsutism + irregular periods = investigate for PCOS
- 6Co-cyprindiol (Dianette): higher VTE risk than standard COCPs
Put your reading into practice
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regional clinical guidance
Acne Vulgaris: guidance by region
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