AKT · Dermatology/Inflammatory & papulosquamous

Acne vulgaris

Pilosebaceous unit: hyperkeratinisation + sebum + C. acnes + inflammation

Overview

A chronic inflammatory disease of the pilosebaceous unit driven by four factors: follicular hyperkeratinisation, androgen-driven sebum excess, Cutibacterium acnes colonisation, and inflammation. The presence of COMEDONES is what separates it from rosacea.

Recognise

Comedones — open (blackheads) and closed (whiteheads) — the non-inflammatory hallmark and the key discriminator from rosacea
Inflammatory papules and pustules; nodules and cysts in severe disease; seborrhoea
Face, back and chest; sequelae are scarring and post-inflammatory hyperpigmentation (especially in skin of colour)

Red flags

Severe nodulocystic/conglobate acne or scarring or major psychological impact → refer; acne fulminans (systemic upset, ulcerating lesions) is an emergency

Differentials & how to tell them apart

RosaceaNO comedones, central face, telangiectasia and flushing, typically age >30

Folliculitisfollicular pustules each centred on a hair, infective, no comedones

Perioral dermatitispapulopustules around the mouth sparing the vermilion border, often steroid-induced

Keratosis pilarisrough follicular papules on the outer upper arms/cheeks, no inflammation

Clinical image

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Acne vulgaris — clinical imagesDermNet

Investigations

Clinical diagnosis and severity grading. Consider an androgen/PCOS screen only if there are features of hyperandrogenism (hirsutism, irregular menses, virilisation).

Management

A 12-week course of a fixed-combination topical regimen (e.g. adapalene + benzoyl peroxide, or benzoyl peroxide + clindamycin)

112-week fixed-combination topical regimen chosen by severity (NICE NG198): adapalene + benzoyl peroxide; OR benzoyl peroxide + clindamycin; OR a topical combination PLUS oral lymecycline/doxycycline for moderate-to-severe disease.Gate: Never use a topical or oral antibiotic as MONOTHERAPY in acne — always combine with benzoyl peroxide or a topical retinoid to limit resistance; and oral tetracyclines are contraindicated in pregnancy and under 12 years (tooth staining)
2Inadequate response at 12 weeks, or moderate-to-severe disease → add an oral tetracycline (or a combined oral contraceptive in women) to the topical regimen; review again at 12 weeks.
3Severe, nodulocystic, scarring, or treatment-resistant → refer for oral isotretinoin under the pregnancy-prevention programme.

Benzoyl peroxide — antibacterial + comedolytic; reduces antibiotic resistance when combined with an antibiotic

Topical retinoid (adapalene) — comedolytic; teratogenic — avoid in pregnancy

Topical antibiotic (clindamycin) — always combined with benzoyl peroxide or a retinoid, never as monotherapy

Azelaic acid — alternative topical, useful in pigmentation

Oral tetracycline (lymecycline, doxycycline) — moderate-severe; not in pregnancy or under 12 years

Combined oral contraceptive — option in women

Oral isotretinoin — specialist; severe/scarring/resistant; teratogenic — pregnancy-prevention programme

Key points

Isotretinoin is teratogenic and needs the pregnancy-prevention programme plus lipid/LFT and mood monitoring. Consider PCOS if hyperandrogenic features. Treatments take 6–8 weeks to show benefit — counsel on adherence.

Monitor & prognosis

Response at 12-week reviews; isotretinoin requires bloods and pregnancy testing.

Usually improves over years; early effective treatment prevents scarring.

Source: NICE NG198; NICE CKS Acne vulgaris