Dermatology · PANCE / PANRE

Acne Vulgaris

Chronic inflammatory disorder of the pilosebaceous unit driven by androgens, sebum, keratinization, and Cutibacterium acnes.

Also known as: acne, comedonal acne, inflammatory acne, nodulocystic acne, pimples

Overview

A chronic inflammatory disorder of the pilosebaceous unit characterized by comedones, papules, pustules, nodules, and cysts, distributed on the face, chest, and back.

Epidemiology

Affects up to 85% of adolescents; peak incidence ages 12-24. Persists into adulthood in ~25% of women and ~12% of men. More severe and scarring forms in male adolescents.

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Risk factors

Adolescence and pubertal androgen surge
Family history of acne
Polycystic ovary syndrome (PCOS), congenital adrenal hyperplasia, other hyperandrogenism
Medications: anabolic steroids, lithium, phenytoin, isoniazid, high-dose B12, corticosteroids (steroid acne)
Mechanical occlusion (helmets, headbands), comedogenic cosmetics
High glycemic load diet and dairy (weak association)

Pathophysiology

Four-step pathogenesis: (1) androgen-driven sebum overproduction, (2) follicular hyperkeratinization → microcomedone, (3) proliferation of Cutibacterium (Propionibacterium) acnes within the lipid-rich follicle, (4) innate immune activation via TLR-2 → perifollicular inflammation. Rupture of distended follicles spills contents into the dermis, producing inflammatory papules, pustules, nodules, and scarring.

Clinical presentation

Symptoms

Visible facial, chest, or back lesions; mild tenderness with inflammatory papules and nodules
Psychosocial distress, anxiety, depression — disproportionate to objective severity in many patients
Post-inflammatory hyperpigmentation in skin of color; erythema and scarring after resolution

Signs / physical exam

Open comedones (blackheads) — dilated follicles with oxidized keratin plug
Closed comedones (whiteheads) — small flesh-colored papules with intact follicular orifice
Inflammatory papules and pustules
Nodules and cysts (>5 mm) — risk of permanent scarring
Ice-pick, boxcar, or rolling atrophic scars; hypertrophic/keloid scars on chest, back, jaw

Classic findings

Mixed comedonal and inflammatory lesions in seborrheic distribution (forehead, nose, cheeks, chin, upper chest and back).

Differential diagnosis

Rosacea — Centrofacial erythema and telangiectasias, NO comedones, triggers include heat/alcohol/spice; onset typically age 30-50
Perioral dermatitis — Small papules/pustules around mouth sparing the vermilion border; often history of topical steroid use
Folliculitis (bacterial or Pityrosporum) — Monomorphous follicular pustules, often on trunk/shoulders; Pityrosporum responds to antifungals, not antibiotics
Acne fulminans / acne conglobata — Severe nodulocystic disease with fever, arthralgia, leukocytosis (fulminans); interconnected sinus tracts (conglobata)
Hidradenitis suppurativa — Painful nodules and sinus tracts in axillae, groin, inframammary folds; no comedones except double-headed open comedones
Drug-induced acneiform eruption — Sudden monomorphic eruption after steroids, EGFR inhibitors, lithium, isoniazid; no true comedones
Keratosis pilaris — Rough follicular papules on extensor arms, thighs, cheeks; no inflammation or pustules

Diagnostic workup

Diagnostic criteria

Clinical diagnosis based on lesion morphology and distribution. Severity graded as mild (comedonal ± few inflammatory papules), moderate (numerous papules/pustules ± few nodules), or severe (widespread nodulocystic disease, scarring, or failure of prior therapy).

Labs

Generally clinical diagnosis — no routine labs
If suspect hyperandrogenism (sudden severe acne, hirsutism, menstrual irregularity, alopecia): total/free testosterone, DHEAS, 17-OH progesterone, LH/FSH ratio, prolactin
Baseline LFTs and lipid panel before starting isotretinoin; pregnancy testing per iPLEDGE program

Imaging

Not indicated for routine acne
Pelvic ultrasound if PCOS suspected

Diagnostic algorithm

Severity	Lesion Profile	Stepwise Therapy
Mild comedonal	Open/closed comedones, few papules	Topical retinoid ± BPO
Mild-moderate inflammatory	Numerous papules/pustules	Topical retinoid + BPO + topical antibiotic
Moderate	Papules, pustules, few nodules, truncal involvement	Above + oral antibiotic (doxycycline) ± hormonal therapy (women)
Severe / scarring / refractory	Widespread nodulocystic, sinus tracts, scarring	Oral isotretinoin (iPLEDGE) ± short steroid course

Severity-based stepwise therapy for acne vulgaris (AAD 2024).

Treatment

First-line

Mild comedonal: topical retinoid — tretinoin 0.025-0.1%, adapalene 0.1-0.3%, tazarotene 0.05-0.1% (apply at night; avoid in pregnancy except adapalene category C; start every other night to limit irritation)
Mild-moderate inflammatory: benzoyl peroxide 2.5-10% ± topical antibiotic — clindamycin 1%, erythromycin 2% (always combine antibiotic with BPO to prevent resistance)
Fixed-dose combinations: adapalene/BPO, clindamycin/BPO, clindamycin/tretinoin improve adherence
Moderate: add oral antibiotic for 3-4 months — doxycycline 50-100 mg BID or minocycline 50-100 mg BID (sarecycline as alternative); avoid in children <8 yrs and pregnancy
Hormonal therapy in women: combined oral contraceptive (norgestimate/ethinyl estradiol, drospirenone/EE) or spironolactone 50-200 mg/day (monitor K+, avoid in pregnancy — teratogenic)

Severe nodulocystic / scarring / treatment-refractory

Oral isotretinoin 0.5-1.0 mg/kg/day × 5-7 months, cumulative dose 120-150 mg/kg
iPLEDGE enrollment required — monthly pregnancy tests and 2 forms of contraception in females of reproductive potential
Monitor LFTs, lipids, CBC at baseline and during therapy; counsel on dryness, photosensitivity, depression/mood changes, IBD signal (debated)

Acne fulminans

Systemic corticosteroids (prednisone 0.5-1 mg/kg/day) for 4-6 weeks, then overlap with low-dose isotretinoin starting at 0.1 mg/kg/day and titrate

Second-line / adjunct

Topical clascoterone 1% cream BID — first topical androgen receptor inhibitor approved for acne
Topical dapsone 5-7.5% — useful in adult female acne
Azelaic acid 15-20% — antimicrobial, anti-inflammatory, brightening (helpful for PIH)
Intralesional triamcinolone 2.5-5 mg/mL for individual nodules/cysts
Procedural: chemical peels, light/laser therapy, comedone extraction; scar revision with subcision, microneedling, fractional laser, dermabrasion, fillers

Complications

Permanent scarring (atrophic, hypertrophic, keloid)
Post-inflammatory hyperpigmentation, especially in Fitzpatrick IV-VI skin
Depression, anxiety, body dysmorphic disorder, suicidality
Isotretinoin teratogenicity (microtia, CNS, cardiac malformations)
Tetracycline-class adverse effects: photosensitivity, pseudotumor cerebri, esophagitis, vestibular toxicity (minocycline), drug-induced lupus and pigmentation (minocycline)

PANCE pearls

Comedones are the pathognomonic primary lesion of acne — their absence should prompt reconsideration of the diagnosis (especially rosacea or folliculitis).
Never combine isotretinoin with tetracyclines — risk of pseudotumor cerebri.
Spironolactone is the most underused effective therapy for adult female acne; do not require routine K+ monitoring in healthy young women on stable doses (AAD 2024 update).
Topical retinoids are foundational at every severity tier and during maintenance — do not stop them when adding other therapies.
Sudden-onset severe acne with hirsutism or virilization in an adult woman warrants endocrine workup for ovarian or adrenal tumor.

References

AAD 2024 — Guidelines of Care for the Management of Acne Vulgaris (Reynolds et al., J Am Acad Dermatol 2024)
Global Alliance 2018 — Practical Management of Acne for Clinicians: An International Consensus from the Global Alliance to Improve Outcomes in Acne (Thiboutot et al., J Am Acad Dermatol 2018)
iPLEDGE — iPLEDGE Risk Evaluation and Mitigation Strategy (REMS) Program — US FDA

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