Overview
Acne Vulgaris
1. Clinical Overview
Summary
Acne vulgaris is a chronic inflammatory disease of the pilosebaceous unit (hair follicle and sebaceous gland). It affects over 80% of adolescents and can persist into adulthood in 20-40% of cases. The pathophysiology involves four key factors: excess sebum production, follicular hyperkeratinisation, Cutibacterium acnes colonisation, and inflammation. Management is stepwise: topical retinoids and benzoyl peroxide for mild acne, adding oral antibiotics for moderate disease, and isotretinoin for severe or scarring acne. The psychological impact is often severe and disproportionate to clinical severity.
Key Facts
- Definition: Chronic inflammatory disease of the pilosebaceous unit
- Prevalence: 80-90% of adolescents; 20-40% persist into adulthood
- Peak age: 14-19 years
- Key pathogen: Cutibacterium acnes (formerly Propionibacterium acnes)
- Key treatment: Topical retinoids are foundation; isotretinoin is most effective for severe acne
- Psychological impact: Significant; associated with anxiety, depression, low self-esteem
Clinical Pearls
The 4 Factors: Acne pathophysiology = Seborrhoea (excess oil) + Hyperkeratosis (blocked pores) + Bacteria (C. acnes) + Inflammation. Isotretinoin is the only treatment that addresses all four.
Patience Is Key: Explain to patients that treatments take 8-12 weeks to show benefit. Set expectations early to improve adherence.
Never Antibiotic Monotherapy: Always combine oral antibiotics with topical retinoid/benzoyl peroxide to prevent resistance. Limit antibiotics to 3-6 months maximum.
Why This Matters Clinically
Acne is extremely common and has significant psychological morbidity including depression and social withdrawal. Early effective treatment prevents scarring, which is permanent. NICE and AAD guidelines have standardised stepwise management. Isotretinoin requires careful monitoring due to teratogenicity and mood effects.
2. Epidemiology
Incidence & Prevalence
- Prevalence: 80-90% of adolescents affected at some point
- Adult acne: 20-40% have persistent acne into 30s-40s
- Female predominance: In adults, females more commonly affected
Demographics
| Factor | Details |
|---|---|
| Age | Peak 14-19 years; can occur at any age |
| Sex | Adolescents: equal; Adults: Female > Male |
| Ethnicity | More severe in darker skin types; higher risk of post-inflammatory hyperpigmentation |
| Geography | Worldwide; possibly lower in rural non-Western populations |
Risk Factors
Non-Modifiable:
- Puberty (hormonal changes)
- Family history (strong genetic component)
- Ethnicity (darker skin prone to PIH)
Modifiable:
| Risk Factor | Relative Risk |
|---|---|
| High glycaemic index diet | 1.5-2x (associated, not proven causal) |
| Dairy consumption | 1.2-1.5x (skim milk association) |
| Cosmetics (comedogenic) | Variable |
| Mechanical friction (helmets, straps) | Localised acne mechanica |
| Anabolic steroids | High risk of severe acne |
3. Pathophysiology
Mechanism
Step 1: The Hormonal Trigger (Seborrhoea)
- Androgens: At puberty, DHEA-S and Testosterone surge.
- The Sebaceous Gland: Highly sensitive to Dihydrotestosterone (DHT) via Type I 5α-reductase.
- Result: Massive increase in sebum (oil) production. "Fuel for the fire".
Step 2: The Plug (Hyperkeratinisation)
- Normal: Follicular keratinocytes shed loosely and exit the pore.
- Pathology: In acne, they become sticky (Hyperkeratosis). They clump together with sebum to form a solid plug.
- The Microcomedone: The invisible precursor to all acne lesions.
Step 3: The Coloniser(C. acnes)
- The Bacteria: Cutibacterium acnes is a normal commensal anaerobe.
- Overgrowth: It thrives in the oxygen-free, lipid-rich environment of the blocked comedone.
- Biofilm: It forms a biofilm, making it resistant to treatment.
Step 4: The Explosion (Inflammation)
- Immune Activation: C. acnes releases lipases (breaking sebum into irritating fatty acids) and chemotactic factors.
- Rupture: The distended follicle wall bursts into the dermis.
- Response: Neutrophils and Macrophages rush in -> Pustules and Cysts.
- Resolution: If damage is deep (dermal), healing occurs via fibrosis -> SCARRING.
Classification
| Type | Definition | Clinical Features |
|---|---|---|
| Comedonal | Non-inflammatory; blocked pores | Open comedones (blackheads), closed comedones (whiteheads) |
| Papulopustular | Inflammatory | Red papules, pustules with central pus |
| Nodulocystic | Severe inflammatory | Deep nodules, cysts, high scar risk |
| Acne conglobata | Severe interconnected nodulocystic | Abscesses, sinus tracts, severe scarring |
| Acne fulminans | Systemic; medical emergency | Ulcerative lesions + fever + arthralgia |
Anatomical/Physiological Considerations
- Pilosebaceous units are concentrated on face, chest, and back (seborrhoeic areas)
- Sebaceous glands are androgen-dependent
- Scarring occurs when inflammation extends beyond the dermis
- Darker skin types have higher risk of keloid scarring and post-inflammatory hyperpigmentation (PIH)
4. Clinical Presentation
Symptoms
Typical Presentation:
Atypical Presentations:
Signs
Red Flags
[!CAUTION] Red Flags — Seek urgent input if:
- Depression or suicidal ideation (assess before and during isotretinoin)
- Acne fulminans (systemic symptoms: fever, joint pain, ulceration) — needs steroids
- Signs of hyperandrogenism: hirsutism, menstrual irregularity, androgenic alopecia (check for PCOS/CAH)
- Drug-induced acne (steroids, androgens, lithium, phenytoin)
- Rapid onset severe acne in adult (consider secondary cause)
Facial spots (99%) — most common site
Common presentation.
Back and chest involvement (50-60%)
Common presentation.
Oiliness of skin (seborrhoea)
Common presentation.
Pain with nodular lesions
Common presentation.
Distress regarding appearance (very common)
Common presentation.
5. Clinical Examination
Structured Approach
General:
- Psychological impact (ask about mood, self-esteem, social avoidance)
- Check for signs of hyperandrogenism (females)
Skin Examination:
- Distribution: face (forehead, cheeks, chin, nose), chest, back
- Lesion types: comedones, papules, pustules, nodules, cysts
- Count lesions (for severity grading and monitoring)
- Scars: type (ice-pick, boxcar, rolling, keloid) and extent
- Post-inflammatory changes (PIH, erythema)
Special Tests
| Test | Technique | Positive Finding | Sensitivity/Specificity |
|---|---|---|---|
| Clinical grading (Leeds/FDA) | Count lesions; assess predominant type | Mild/Moderate/Severe | Used for monitoring response |
| DLQI (Dermatology Life Quality Index) | Questionnaire | Score > 10 = major impact on life | Standard QoL assessment |
| PHQ-9 (Mood screen) | Questionnaire | Score ≥ 10 = moderate depression | Baseline before isotretinoin |
6. Investigations
First-Line (Bedside)
- Clinical diagnosis — No investigations needed for typical acne
- Mood assessment — Before starting isotretinoin
Laboratory Tests
| Test | Expected Finding | Purpose |
|---|---|---|
| Pregnancy test | Negative | Before isotretinoin; monthly during |
| LFTs | Normal | Baseline and 8 weeks on isotretinoin |
| Fasting lipids | Normal | Baseline and 8 weeks on isotretinoin |
| Testosterone, SHBG, LH, FSH | May be abnormal in PCOS | Only if hyperandrogenism suspected |
Imaging
| Modality | Findings | Indication |
|---|---|---|
| Pelvic USS | Polycystic ovaries | If PCOS suspected |
| Not routinely indicated | — | — |
Diagnostic Criteria
- Clinical diagnosis based on characteristic lesion morphology and distribution
- No formal diagnostic criteria required
- Grading systems (Leeds, FDA, IGA) used for severity assessment
7. Management
Management Algorithm
Patient with Acne
↓
┌─────────────────────────────────────────────────────┐
│ ASSESS SEVERITY │
│ - Mild: Comedonal / Few papules │
│ - Moderate: Many papules / Pustules / Few Nodules │
│ - Severe: Nodulocystic / Scarring / Psychological │
└─────────────────────────┬───────────────────────────┘
↓
┌───────────┴───────────┐
↓ ↓
MILD/COMEDONAL MODERATE/PAPULAR
(Topical Therapy) (Add Oral Therapy)
↓ ↓
┌─────────────────────────┐ ┌─────────────────────────┐
│ FIRST LINE: │ │ FIRST LINE: │
│ Top Retinoid (Adapalene)│ │ Top Retinoid + BP │
│ + │ │ + │
│ Benzoyl Peroxide (BP) │ │ Oral Lymecycline │
│ │ │ (Max 3-6 months) │
└─────────────┬───────────┘ └────────────┬────────────┘
│ │
│ (Review 12w) │
└───────────┬───────────────┘
↓
Response Poor?
↓
┌───────────┴───────────┐
↓ ↓
FEMALE (Hormonal) SEVERE (Fail/Scarring)
↓ ↓
┌───────────────────┐ ┌─────────────────────┐
│ CONSIDER: │ │ REFER DERMATOLOGY: │
│ - COCP (Dianette) │ │ Oral Isotretinoin │
│ - Spironolactone │ │ ("Roaccutane") │
└───────────────────┘ └─────────────────────┘
Conservative Management
- Gentle skin cleansing (lukewarm water, non-comedogenic cleanser)
- Avoid picking/squeezing (worsens scarring)
- Non-comedogenic moisturisers and sunscreen
- Dietary modification (low GI diet may help; limited evidence)
- Psychological support and reassurance
Medical Management
1. The Foundation: Topicals (All severities)
- Retinoids (Adapalene/Tretinoin): Normalise keratinisation. Prevent microcomedones. Must be continued for maintenance.
- Benzoyl Peroxide (BPO): Antimicrobial (oxidising agent - no resistance) + Keratolytic.
- Combination (Epiduo): Gold standard topical. Retinoid + BPO.
2. The Step Up: Oral Antibiotics (Moderate)
- Lymecycline / Doxycycline: Anti-inflammatory + Antibacterial.
- Rules:
- Never monotherapy (Must use topical BPO to prevent resistance).
- Limit to 3-6 months.
- If no response at 3m -> Switch or Refer.
3. Hormonal Options (Females)
- COCP (Dianette/Yasmin): Anti-androgenic. Good for flare prevention.
- Spironolactone (Off-label): 50-100mg OD. Blocks androgen receptor.
- Indication: Adult female acne, PCOS, jawline distribution.
- Monitor: Potassium/Renal function (rarely needed in young healthy females).
- Contraindication: Pregnancy (Feminisation of male fetus).
4. The "Nuclear" Option: Oral Isotretinoin
- Mechanism: Systemic Retinoid. The ONLY drug that hits all 4 pathogenic factors.
- Dosing: 0.5-1.0 mg/kg/day. Target Cumulative Dose: 120-150 mg/kg (to prevent relapse).
- Course Length: 4-6 months typically.
- The "Pregnancy Prevention Programme" (PPP/iPLEDGE):
- Highly Teratogenic (Category X).
- Females MUST be on effective contraception (often 2 forms).
- Monthly pregnancy tests required.
Isotretinoin Monitoring
| Parameter | Timing | Rationale |
|---|---|---|
| Pregnancy Test | Monthly | Mandatory legal requirement (PPP) |
| Lipids | Baseline, 1m, Dose change | Causes hypertriglyceridaemia |
| LFTs | Baseline, 1m, Dose change | Can cause hepatotoxicity |
| Mood (PHQ-9) | Every visit | Rare association with depression |
| Creatine Kinase | If muscle pain | Can cause rhabdomyolysis (rare) |
Disposition
- Primary Care: Manage Mild-Moderate. Trial of Topicals -> Trial of ABx -> Trial of COCP.
- Dermatology Referral:
- Severe Nodulocystic Acne (Isotretinoin needed immediately).
- Scarring (at any stage).
- Failure of 2 courses of antibiotics.
- Diagnostic uncertainty.
8. Complications
Immediate (Minutes-Hours)
| Complication | Incidence | Presentation | Management |
|---|---|---|---|
| Acne fulminans | Rare | Ulceration, fever, arthralgia | Systemic steroids + isotretinoin |
Early (Days-Weeks)
- Treatment irritation: Dryness, peeling, redness from retinoids/BP — reduce frequency, moisturise
- Photosensitivity: With doxycycline — advise sun protection
Late (Weeks-Months-Years)
- Scarring: Ice-pick (deep narrow), boxcar (wide depressed), rolling (undulating), keloid (raised overgrowth)
- Post-inflammatory hyperpigmentation (PIH): Dark marks; especially in darker skin
- Post-inflammatory erythema (PIE): Red marks; especially in lighter skin
- Psychological sequelae: Anxiety, depression, body dysmorphia, social withdrawal
- Isotretinoin side effects: Dry lips (100%), dry eyes, epistaxis, raised lipids, mood changes (rare)
9. Prognosis & Outcomes
Natural History
- Adolescent acne typically improves by early 20s
- 20-40% have persistent acne into adulthood
- Untreated nodulocystic acne leads to permanent scarring
Outcomes with Treatment
| Variable | Outcome |
|---|---|
| Response to topical therapy (mild) | 60-70% improvement |
| Response to oral antibiotics (moderate) | 70-80% improvement |
| Response to isotretinoin (severe) | 85-95% clearance |
| Relapse after isotretinoin | 20-30% (may need 2nd course) |
| Scar improvement | Requires procedures (laser, subcision, fillers) |
Prognostic Factors
Good Prognosis:
- Early treatment initiation
- Mild disease
- Good treatment adherence
- No family history of scarring
Poor Prognosis:
- Delayed presentation
- Nodulocystic disease
- Family history of severe acne/scarring
- Darker skin type (higher PIH risk)
- Poor adherence
10. Evidence & Guidelines
Key Guidelines
- NICE NG198 (2021) — Acne vulgaris: management. Key recommendations: limit antibiotic duration to 3 months; never use antibiotic monotherapy; topical retinoid is foundation of treatment. NICE NG198
- AAD Guidelines (2016) — Guidelines of care for the management of acne vulgaris. American Academy of Dermatology. AAD
- European Evidence-Based Guidelines (2016) — European Dermatology Forum. EDF Guidelines
Landmark Trials
Cochrane Review: Oral Isotretinoin (2018) — Systematic review of isotretinoin efficacy
- Key finding: Isotretinoin is highly effective for severe acne; 85-95% achieve remission
- Clinical Impact: Established isotretinoin as gold standard for severe disease
Cochrane Review: Topical Retinoids (2019) — Systematic review
- Key finding: Topical retinoids effective for comedonal and inflammatory acne
- Clinical Impact: Confirmed retinoids as first-line for maintenance
NICE Evidence Review (2021) — Duration of oral antibiotics
- Key finding: Limiting antibiotics to 3 months reduces resistance with similar efficacy
- Clinical Impact: Changed practice to shorter antibiotic courses
Evidence Strength
| Intervention | Level | Key Evidence |
|---|---|---|
| Topical retinoids | 1a | Cochrane review |
| Benzoyl peroxide | 1a | Meta-analyses |
| Oral antibiotics + topical | 1b | RCTs |
| Isotretinoin | 1a | Cochrane review |
| Low GI diet | 2b | Observational + small RCTs |
11. Patient/Layperson Explanation
What is acne?
Acne ("spots") happens when the tiny holes in your skin (pores) that contain hair follicles and oil glands become blocked. Oil builds up behind the blockage, bacteria grow in the blocked pore, and this causes redness and inflammation. It is NOT caused by poor hygiene — the problem is inside the skin, not on the surface.
Why does it matter?
Acne can cause permanent scars if not treated properly, especially the deep painful spots. It can also significantly affect how you feel about yourself. It is a real medical condition that deserves treatment.
How is it treated?
- Creams and gels (topicals): These unblock pores (retinoids like adapalene) and kill bacteria (benzoyl peroxide). They take 2-3 months to work properly.
- Antibiotic tablets: Added if creams alone are not enough. Used for a maximum of 3-6 months alongside creams.
- Roaccutane (isotretinoin): The most effective treatment for severe acne. Shrinks oil glands permanently. Requires careful monitoring because of side effects and it causes severe birth defects if taken during pregnancy.
What to expect
- All treatments take 8-12 weeks to show benefit — do not give up early
- Your skin may get slightly worse initially (purging) with retinoids — this is normal
- Dryness and peeling are common; use moisturiser
- If you have severe acne, you will likely be referred to a skin specialist (dermatologist)
When to seek help
See your doctor if:
- Your spots are deep, painful, or leaving scars
- Over-the-counter treatments have not worked after 2-3 months
- You are feeling low, anxious, or depressed because of your skin
- You have other symptoms like excess hair, irregular periods (females)
12. References
Primary Guidelines
- National Institute for Health and Care Excellence. Acne vulgaris: management (NG198). 2021. NICE NG198
- Zaenglein AL, et al. Guidelines of care for the management of acne vulgaris. J Am Acad Dermatol. 2016;74(5):945-973. PMID: 26897386
Key Trials
- Costa CS, et al. Oral isotretinoin for acne. Cochrane Database Syst Rev. 2018;11(11):CD009435. PMID: 30484284
- Leyden J, et al. Why topical retinoids are mainstay of therapy for acne. Dermatol Ther (Heidelb). 2017;7(3):293-304. PMID: 28585192
- Nast A, et al. European evidence-based (S3) guideline for the treatment of acne. J Eur Acad Dermatol Venereol. 2016;30 Suppl 8:8-29. PMID: 27921404
Further Resources
- British Association of Dermatologists: bad.org.uk/patient-information
- DermNet NZ: dermnetnz.org/acne
- Acne Support: acnesupport.org.uk
13. Examination Focus
The "Dermatology" Station
1. Inspect (The 3 S's)
- Sites: Face, Chest, Back? (Ask to examine trunk - often missed).
- Severity:
- Mild: Comedones predom.
- Moderate: Papules/Pustules.
- Severe: Nodules/Cysts.
- Scarring: Look closely.
- Ice Pick: Deep, narrow holes.
- Boxcar: Punch-out depressions.
- Keloid: Lumpy jawline/chest.
- Presence of scarring = Indication for Isotretinoin.
2. Assess Impact
- "How does this affect your life?" (DLQI).
- Look for signs of depression (flat affect, poor eye contact).
Viva Questions:
- Q: Why do we limit antibiotics?
- A: To prevent antimicrobial resistance (antibiotic stewardship). Maximum 3-6 months.
- Q: What are the absolute contraindications to Isotretinoin?
- A: Pregnancy, Breastfeeding, Hepatic impairment, Peanut Allergy (capsules contain arachis oil/soya).
- Q: Explain the mechanism of Benzoyl Peroxide.
- A: It releases free oxygen radicals which kill the anaerobic C. acnes. It is also keratolytic (unblocks pores).
- Q: A 25F has acne + hirsutism + irregular periods. Diagnosis?
- A: Polycystic Ovarian Syndrome (PCOS). Check Free Androgen Index (FAI) and Pelvic Ultrasound.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Consult a dermatologist for persistent or severe acne.