GPAtlas🧭 When to suspect
Acne vulgaris is a chronic inflammatory disorder of the pilosebaceous unit, driven by four processes acting together: increased sebum production, abnormal follicular keratinisation, colonisation with Cutibacterium acnes (formerly Propionibacterium acnes), and inflammation. It usually begins around puberty (from about age 12) and most often affects the face, though the chest, shoulders and upper back are commonly involved. Lesions are characteristically polymorphic – a mixture of non-inflammatory comedones (blackheads and whiteheads) and inflammatory papules, pustules, nodules and cysts.
Suspect acne in any adolescent or young adult with this pattern, and ask about oily skin, a family history of acne, and aggravating factors. The two skills that matter most in primary care are to grade severity accurately – because management is driven almost entirely by severity – and to recognise the impact on mental health, which does not track the appearance of the skin.
| Lesion pattern | NICE classification | First-line approach |
|---|---|---|
| Predominantly comedones with few papules/pustules | Mild to moderate (≤34 inflammatory lesions, ≤2 nodules) | 12-week course of a topical fixed-combination |
| Widespread papules and pustules, ± a few nodules | Mild-to-moderate or moderate-to-severe by lesion count | Topical fixed-combination, ± oral antibiotic if moderate-to-severe |
| Numerous inflammatory lesions, ≥3 nodules, cysts or scarring | Moderate to severe (≥35 inflammatory lesions or ≥3 nodules) | Topical + oral antibiotic; consider referral and isotretinoin |
| Sudden ulcerating/crusting nodules with systemic upset | Acne fulminans | Same-day on-call dermatology (within 24 hours) |
Most acne settles by the early-to-mid twenties, but it can persist into the thirties and forties. A first presentation, or treatment-resistant acne, in an adult woman should prompt thought about hyperandrogenism and PCOS.
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🧠 Clinical pearl Comedones are the diagnostic hallmark of acne. If a patient has inflammatory papules and pustules but no comedones, question the diagnosis: rosacea brings flushing and telangiectasia (and no comedones), perioral dermatitis characteristically spares the skin immediately around the lips, and monomorphic pustules in someone on long-term antibiotics suggest Gram-negative folliculitis. |
Source: NICE NG198
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