Acne vulgaris
A disorder of the pilosebaceous unit in which follicular hyperkeratinisation blocks the pore, androgen-driven sebum feeds Cutibacterium acnes, and the resulting inflammation produces comedones, papules, pustules and, in severe disease, scarring.
In a nutshell
Follicular hyperkeratinisation blocks the pore, androgen-driven sebum accumulates and feeds Cutibacterium acnes, and the ensuing inflammatory response produces the visible lesions. Treatment climbs a ladder that targets keratinisation, sebum, bacteria and inflammation in turn.
Classic presentation
A teenager with comedones, papules and pustules across the face, chest and back, fluctuating in severity.
Key points
- The first event is a keratin plug (comedone), not bacterial infection: C. acnes proliferation and inflammation come afterwards.
- Androgens drive sebum production, which is why acne peaks at puberty and can signal PCOS if accompanied by hirsutism or irregular periods.
- Never use a topical or oral antibiotic alone; always combine with benzoyl peroxide to limit antimicrobial resistance.
- Isotretinoin is unique among acne treatments in acting on all four mechanistic steps at once, hence its efficacy in severe disease.
- Acne fulminans (sudden severe ulcerating acne with systemic upset) is an emergency needing urgent specialist input.
First-line investigation
None routinely: acne is a clinical diagnosis based on lesion type and distribution. Investigate for hyperandrogenism only if clinically suggested.
First-line management
A topical retinoid combined with benzoyl peroxide, normalising keratinisation and reducing C. acnes and inflammation.
Exam traps
- Antibiotic monotherapy (topical or oral) is a wrong answer; it must be paired with benzoyl peroxide.
- Psychological impact does not correlate reliably with visible severity, so distress alone can justify escalation.
- Rapid-onset severe acne with hirsutism and irregular periods in a woman should prompt PCOS work-up, not just topical treatment.
Educational content pending clinical review. Not medical advice.