Post-Acne Scar Management

1. Classification of Post-Acne Scars

2. Step 1 - Control Active Acne First

3. Management by Scar Type

A. Post-Inflammatory Hyperpigmentation (PIH)

1. Increased epidermal melanocyte activity
2. Dermal melanosis (melanin dropout into dermis - gives a gray hue)

• Hydroquinone (4-6%) - first-line depigmenting agent; more effective for epidermal PIH
• Tretinoin - enhances hydroquinone's effect and has independent depigmenting action
• Chemical peels (glycolic acid, salicylic acid) - used with caution; unpredictable results in darker skin; can worsen pigmentation
• Laser treatments - must be performed with extreme caution in darker phototypes; increased pigmentation can result

Post-inflammatory hyperpigmentation - Andrews' Diseases of the Skin

B. Atrophic Scars (Ice-pick, Boxcar, Rolling)

Topical Agents

• Retinoids (tretinoin, adapalene): stimulate collagen synthesis and epidermal turnover; modest improvement in shallow scars
• Alpha-hydroxy acids (AHAs): glycolic acid peels decrease corneocyte cohesion and improve scar texture

Chemical Peels

• Glycolic acid (20-70%), salicylic acid, trichloroacetic acid (TCA), phenol peels
• Improve surface irregularities; deeper peels for deeper scars; risk of PIH in darker skin
• Dermatology 2-Volume Set 5e: "Low-concentration chemical peels are beneficial... Common peeling agents include AHAs (including glycolic acid), salicylic acid, and trichloroacetic acid."

Microneedling / Dermaroller

• Induces collagen neogenesis via controlled micro-injury
• Safe across all skin phototypes (low PIH risk compared to ablative lasers)
• Effective for rolling and boxcar scars; multiple sessions required

Laser Resurfacing

• Laser penetration should be 50-75% of scar depth
• Ablative fractional lasers induce robust tissue remodeling for hypertrophic/contracted scars
• Non-ablative fractional lasers improve texture with less downtime; can be supplemented with prostaglandin analogues (e.g., bimatoprost + tretinoin)
• Individuals with darker skin phototypes are at higher risk of PIH post-laser

Dermabrasion

• Mechanical resurfacing; historically used for acne scars
• Largely replaced by fractional lasers in modern practice
• Risk of PIH; contraindicated in active isotretinoin use (traditionally 6-12 month wait, though evidence for this interval is debated)

Soft Tissue Augmentation (Fillers)

• Indicated for discrete depressed scars that improve with stretching
• Agents: poly-L-lactic acid, calcium hydroxylapatite, autologous fat, hyaluronic acid
• Effect is temporary; does not correct the scar itself

Subcision

• Needle or cannula inserted beneath rolling/boxcar scars to release fibrous tethering bands
• Induces collagen deposition; effective for rolling scars
• Often combined with fractional laser or microneedling for additive benefit

C. Ice-Pick Scars (Specific Techniques)

• Punch excision: excise the scar core, then close primarily or with a punch graft
• Punch elevation: lift the base of the scar to the surface level without excision
• TCA CROSS (chemical reconstruction of skin scars): focal application of high-concentration TCA (70-100%) into the scar base; triggers collagen synthesis; multiple sessions

D. Hypertrophic Scars and Keloids

• Intralesional corticosteroids (triamcinolone acetonide 10-40 mg/mL): flatten hypertrophic scars; risk of hypopigmentation and atrophy, especially in darker skin
• Silicone gel sheets: first-line for hypertrophic scar prevention and treatment
• Pulsed-dye laser (PDL): reduces erythema and scar bulk
• Ablative fractional laser: most effective for hypertrophic and contracted scars; induces remodeling
• Full-thickness surgical excision: for larger hypertrophic scars, aggregated pitted scars, and sinus tracts - improves scar placement and cosmetic appearance
• Compression therapy: adjunct for keloid prevention

4. Special Considerations by Skin Phototype

5. Combination Approach (Practical Algorithm)

Active acne controlled?
        ↓ Yes
Assess scar type(s)
        ↓
PIH only → Topical HQ + retinoid ± superficial peel
        ↓
Rolling scars → Subcision + fractional laser/microneedling
        ↓
Boxcar scars → Fractional laser ± microneedling ± filler
        ↓
Ice-pick scars → TCA CROSS and/or punch excision
        ↓
Hypertrophic → Intralesional steroid + silicone + PDL
        ↓
Multiple types → Combined modality (3-6 sessions, 4-8 weeks apart)

6. Emerging / Regenerative Approaches

• Extracellular vesicles and conditioned media - modulate collagen synthesis and wound healing
• Stromal vascular fraction (SVF) and mesenchymal stem cells - autologous cell-based repair These remain investigational but show promise for treatment-resistant atrophic scarring.