Key Facts

Acne vulgaris is a chronic inflammatory condition of the pilosebaceous unit. It is the most common skin condition affecting adolescents and can cause significant psychological morbidity. A systematic stepwise approach is recommended.

Epidemiology

• Affects 80-85% of 11-30 year olds at some point
• Peak prevalence in adolescence; increasingly recognised in adult women (15-20% of women aged 25-40)
• More severe in males (higher androgen levels)
• Significant impact on mental health: associated with depression, anxiety, and reduced self-esteem

Aetiology

• Androgens: stimulate sebaceous gland activity at puberty (testosterone, DHT)
• Genetic factors: strong familial tendency; polygenic inheritance
• Environmental: some evidence for high glycaemic index diet, dairy products
• Medications: corticosteroids, lithium, phenytoin, anabolic steroids
• Conditions: PCOS (androgen excess), Cushing syndrome

Pathophysiology

• Sebum overproduction: androgen-driven increase in sebum secretion from sebaceous glands
• Follicular hyperkeratinisation: abnormal keratinisation of the follicular infundibulum causes microcomedone formation (earliest lesion)
• C. acnes proliferation: anaerobic bacterium thrives in sebum-rich, blocked follicles; triggers innate immune response via TLR-2
• Inflammation: IL-1, TNF-α, and neutrophil recruitment cause papules, pustules, nodules, and cysts
• Comedones → inflammatory papules/pustules → nodules/cysts → scarring

Lesion Types

• Non-inflammatory: open comedones (blackheads), closed comedones (whiteheads)
• Inflammatory: papules (<5mm, red), pustules (papule with visible pus)
• Severe inflammatory: nodules (>5mm, deep, painful), cysts (fluctuant, may discharge)
• Post-inflammatory: hyperpigmentation, erythema, scarring (ice-pick, boxcar, rolling)

Distribution

• Face (99%), back (60%), chest (15%)
• Follows distribution of pilosebaceous units

Severity Classification

• Mild: predominantly comedonal ± few inflammatory lesions
• Moderate: widespread comedones with multiple papules and pustules
• Severe: nodules, cysts, widespread involvement, scarring

Red Flags

• Severe nodulocystic acne — risk of permanent scarring; early isotretinoin referral
• Acne fulminans: sudden onset severe acne with systemic symptoms (fever, arthralgia, myalgia) — urgent dermatology
• Significant psychological distress or suicidal ideation — assess and manage accordingly
• Signs of hyperandrogenism in females (hirsutism, oligomenorrhoea, virilisation) — investigate for PCOS/androgen-secreting tumour
• Prepubertal acne — investigate for precocious puberty or adrenal pathology

Bedside

• Clinical diagnosis — no investigations required for typical acne
• Assess severity (mild/moderate/severe)
• Assess psychological impact (PHQ-9 if depression suspected)
• Document lesion types and distribution

Bloods

• Not routinely required
• Hormonal profile (testosterone, DHEAS, LH, FSH): if hyperandrogenism suspected in females
• Pregnancy test: before starting isotretinoin or co-cyprindiol
• Liver function, lipids: before and during isotretinoin (1 month, then 3-monthly)

Imaging

• Pelvic USS: if PCOS suspected

Special Tests

• Not required for typical acne
• Skin swab: if gram-negative folliculitis suspected (rare, occurs after prolonged antibiotic use)

Non-pharmacological

• Gentle cleanser (avoid scrubs, abrasive products)
• Non-comedogenic skincare and makeup
• Sun protection (especially with retinoids and doxycycline)
• Avoid picking/squeezing lesions
• Dietary advice: limited evidence but consider reducing high-GI foods and dairy
• Psychological support: address impact on self-esteem and mental health

Pharmacological (NICE NG198 — 12-week treatment courses)

Mild acne:

• First-line: fixed-dose combination adapalene 0.1%/benzoyl peroxide 2.5% gel (Epiduo) OD
• Alternative: topical retinoid (adapalene 0.1% or tretinoin 0.025%) alone, or benzoyl peroxide 5% alone
• Topical azelaic acid 20% BD: alternative for sensitive skin or pregnancy

Moderate acne:

• Topical combination (as above) PLUS oral antibiotic:
  • Lymecycline 408mg OD (first-line oral antibiotic)
  • Doxycycline 100mg OD (alternative)
  • Duration: 12 weeks maximum (NICE NG198)
  • Always co-prescribe topical retinoid to reduce resistance
• Do NOT use topical and oral antibiotics together

Moderate acne in females:

• Combined oral contraceptive: co-cyprindiol (Dianette — cyproterone acetate 2mg + ethinylestradiol 35mcg) or other COCP with anti-androgenic progestogen
• Can be combined with topical treatments

Severe/nodulocystic or scarring acne:

• Isotretinoin (Roaccutane): 0.5-1mg/kg/day for 16-24 weeks (aim cumulative dose 120-150mg/kg)
  • Specialist-initiated (dermatologist only)
  • Pregnancy prevention programme mandatory: two negative pregnancy tests before starting, monthly pregnancy tests, effective contraception during and for 1 month after
  • Side effects: dry skin/lips (universal), myalgia, raised lipids, raised LFTs, mood changes (monitor)
  • Monitor: LFTs and lipids at baseline, 1 month, then 3-monthly
  • Avoid waxing and skin procedures during treatment
  • Avoid concurrent tetracyclines (risk of benign intracranial hypertension)

Surgical/Procedural

• Chemical peels (salicylic acid, glycolic acid): adjunctive for comedonal acne
• Intralesional triamcinolone: for isolated nodules/cysts
• Acne scar treatment: laser resurfacing, microneedling, subcision (after acne controlled)

Referral Criteria

• Severe or nodulocystic acne: dermatology referral for isotretinoin
• Acne scarring: early referral before significant scarring develops
• Failure of two 12-week courses of treatment: consider referral
• Significant psychological impact
• Suspected underlying endocrine cause

• 80-85% of acne improves spontaneously by age 25
• Mild-moderate acne: responds to topical treatment in >60% within 12 weeks
• Oral antibiotics: improve inflammatory acne in >65% by 12 weeks
• Isotretinoin: leads to complete/near-complete clearance in 85%; relapse rate 20-30% (may need second course)
• Scarring: occurs in approximately 20% of acne patients; risk increases with severity and delay in treatment
• Adult female acne: may be more persistent and treatment-resistant
• Psychological impact: acne-related depression affects up to 40% of acne patients

NICE NG198 Treatment Pathway Summary

Isotretinoin Monitoring