Skin

Acne vulgaris: stepwise treatment

Clinical Overview and When to Suspect Acne Vulgaris

Acne vulgaris → chronic inflammatory disease of the pilosebaceous unit driven by four key pathogenic factors:

Classic patient: adolescent (12–18 years) presenting with comedones, papules, and/or pustules on the face, chest, and back — onset coincides with adrenarche/puberty.

Also suspect in:

Board pearl: Acne in a prepubertal child (<7 years) should prompt evaluation for hyperandrogenism — consider adrenal or gonadal pathology, precocious puberty.

↑ Sebum production (androgen-mediated)

Follicular hyperkeratinization → microcomedo formation

Proliferation of Cutibacterium acnes (formerly Propionibacterium acnes)

Inflammation → papules, pustules, nodules, cysts

Adult women with hormonal acne (jawline/chin predominant, cyclic flares)

Neonatal acne (first weeks of life, self-limited)

Drug-induced acneiform eruptions (corticosteroids, lithium, phenytoin, anabolic steroids)

Presentation Patterns and Key History

Morphologic lesion types (critical for grading severity):

Distribution: face (nearly universal), upper back, chest, shoulders — areas rich in sebaceous glands

History clues:

Next best step: Characterize lesion type + severity → determines treatment tier.

Non-inflammatory: open comedones (blackheads) and closed comedones (whiteheads)

Inflammatory: erythematous papules, pustules

Severe: nodules (≥5 mm, deep, painful), cysts (fluctuant, pus-filled)

Sequelae: post-inflammatory hyperpigmentation (PIH), atrophic or hypertrophic scars

Age of onset, duration, prior treatments and responses

Menstrual history in females — cyclic flares suggest hormonal component

Medications: corticosteroids, progestins, testosterone, DHEA, lithium, isoniazid

Cosmetic/occupational exposures (pomade acne, chloracne)

Family history of severe acne or isotretinoin use

Psychosocial impact — depression, anxiety, social withdrawal

Physical Exam and Severity Classification

Exam approach:

Severity grading (drives stepwise therapy):

Board pearl: Scarring at any severity level is an indication to escalate therapy more aggressively — do not wait for nodules to appear.

Adequate lighting; examine face, neck, chest, back

Identify predominant lesion type: comedonal vs papulopustular vs nodulocystic

Note scarring (ice-pick, rolling, boxcar) — presence accelerates need for aggressive therapy

Look for signs of hyperandrogenism in women: hirsutism, androgenetic alopecia, acanthosis nigricans

Mild: predominantly comedonal ± few papules/pustules; no nodules; no scarring

Moderate: numerous papules/pustules (≈20–50); few nodules possible; mild scarring

Severe: many nodules/cysts; widespread papulopustular lesions; significant scarring risk

Very severe (acne fulminans): sudden explosive onset of nodules with systemic symptoms (fever, arthralgias, ↑ WBC) — rare but emergent

Diagnostic Workup — When Labs and Biopsy Are Needed

Acne vulgaris is a clinical diagnosis — no labs or biopsy are required in typical presentations.

Consider laboratory evaluation when:

Biopsy indications (rare):

Key distinction: Gram-negative folliculitis can mimic acne flare in patients on long-term antibiotics → culture pustule contents.

Prepubertal acne: DHEA-S, total/free testosterone, 17-hydroxyprogesterone (rule out congenital adrenal hyperplasia, adrenal tumor)

Adult female with irregular menses + acne + hirsutism: testosterone, DHEA-S, FSH/LH ratio → PCOS workup; consider pelvic US

Acne resistant to standard therapy: evaluate for hyperandrogenism

Pre-isotretinoin: pregnancy test (×2), fasting lipid panel, hepatic panel, CBC — baseline required before initiation

Atypical morphology — to exclude rosacea, folliculitis, perioral dermatitis, or cutaneous lupus

Persistent lesions unresponsive to therapy

Diagnostic Interpretation and Key Differentials at Workup

Lab interpretation in hormonal acne/PCOS:

Pre-isotretinoin labs:

Culture indications:

Board pearl: Monomorphic pruritic truncal papulopustules in a young adult on antibiotics → think pityrosporum folliculitis, not acne flare.

↑ Free testosterone, ↑ DHEA-S → hyperandrogenism

LH:FSH ratio >2:1 supports PCOS (not required for diagnosis)

↑ 17-hydroxyprogesterone → late-onset congenital adrenal hyperplasia

Pregnancy test must be negative ×2 (separated by ≥30 days)

Fasting triglycerides: isotretinoin causes dose-dependent ↑ TG → risk of pancreatitis if TG >500

Transaminases: monitor for hepatotoxicity

CBC: mild ↓ WBC/platelets rarely clinically significant

Suspect gram-negative folliculitis (sudden flare of pustules around nose/perioral area after months of oral antibiotics)

Suspect Malassezia (pityrosporum) folliculitis: pruritic, monomorphic papules/pustules on trunk, unresponsive to antibiotics → KOH prep shows yeast forms

First-Line Management — Mild Acne

Mild comedonal acne:

— Normalizes follicular keratinization → prevents microcomedo

— Adapalene 0.1% gel available OTC; best tolerated

— Apply pea-sized amount to entire affected area (not spot treatment) at night

— Expect irritation initially → start every other night, increase frequency

Mild papulopustular acne:

— Benzoyl peroxide (BPO) 2.5–5% → bactericidal, does NOT induce resistance

— OR topical antibiotic (clindamycin 1%) — always combine with BPO to prevent C. acnes resistance

Fixed-dose combinations improve adherence:

Next best step: For any acne patient, a topical retinoid should be part of the regimen — it is the backbone of maintenance therapy.

Board pearl: Never use topical antibiotics as monotherapy → guaranteed resistance development.

Topical retinoid (tretinoin, adapalene, tazarotene) — cornerstone of ALL acne therapy

Topical retinoid PLUS topical antimicrobial:

Adapalene/BPO (Epiduo)

Clindamycin/BPO (Duac)

Moderate Acne Management

Moderate papulopustular acne (numerous papules/pustules, limited nodules):

Preferred systemic antibiotics:

Critical principles:

Board pearl: Tetracyclines are photosensitizing (especially doxycycline) — counsel on sun protection. Doxycycline can also cause esophagitis → take upright with full glass of water.

Key distinction: Doxycycline is preferred over minocycline due to better safety profile and lower cost.

Topical retinoid + BPO + systemic antibiotic

Doxycycline 50–100 mg daily (first-line) — anti-inflammatory + antimicrobial

Minocycline 50–100 mg daily (alternative) — slightly higher risk of drug-induced lupus, pseudotumor cerebri, blue-gray skin discoloration

Sarecycline — newer tetracycline, narrow-spectrum

Limit oral antibiotic course to 3–4 months to minimize resistance

Always use with topical retinoid + BPO

Reassess at 3 months: if improving → taper antibiotic, continue topicals for maintenance

If inadequate response → escalate to isotretinoin or hormonal therapy

Severe Acne and Isotretinoin

Severe nodulocystic acne (or moderate acne refractory to oral antibiotics):

— ↓ Sebum production (up to 90%), normalizes keratinization, ↓ C. acnes, anti-inflammatory

Dosing: 0.5–1 mg/kg/day; cumulative target dose 120–150 mg/kg

Side effects:

Board pearl: Isotretinoin + tetracycline = contraindicated due to additive risk of pseudotumor cerebri (↑ intracranial pressure).

Isotretinoin (13-cis-retinoic acid) — only therapy that addresses ALL four pathogenic factors

Typical course: 5–6 months

Relapse rate ~20%; may need second course

Teratogenicity — absolute contraindication in pregnancy (category X)

Mucocutaneous dryness (cheilitis nearly universal), dry eyes, epistaxis

↑ Triglycerides, ↑ LFTs → monitor monthly

Myalgias, arthralgias

Depression/suicidality: controversial association; monitor mood but evidence is not conclusive

Pseudotumor cerebri — do NOT combine with tetracyclines

Special Populations — Hormonal Therapy in Women

Hormonal acne in women (jawline/chin, cyclic premenstrual flares, often with PCOS):

First-line hormonal agents:

— Mechanism: ↑ SHBG → ↓ free testosterone; ↓ adrenal and ovarian androgen production

— Takes 3–6 months for full effect

— Androgen receptor blocker + ↓ androgen synthesis

— Monitor K⁺ (especially with ACEi/ARBs, renal disease)

— Contraindicated in pregnancy (feminization of male fetus) → must use reliable contraception

— Not FDA-approved for acne but widely used off-label

Key distinction: Hormonal therapy is adjunctive — continue topical retinoid + BPO as backbone.

Board pearl: Spironolactone is only for women — do not use in males due to gynecomastia, sexual dysfunction, and feminization.

Combined oral contraceptives (COCs) — FDA-approved: norgestimate/ethinyl estradiol, drospirenone/ethinyl estradiol

Spironolactone 50–200 mg/day

Special Populations — Pregnancy, Pediatrics, Elderly

Pregnancy:

— Topical BPO (category C, considered safe)

— Topical azelaic acid 15–20% (category B — excellent choice)

— Topical erythromycin or clindamycin (with BPO)

— Oral erythromycin (if systemic antibiotic needed, but GI side effects common)

Pediatrics:

Elderly:

Board pearl: Azelaic acid is the go-to for acne in pregnancy — safe and also treats PIH.

Absolutely contraindicated: isotretinoin (category X), tazarotene, oral tetracyclines, spironolactone, COCs

Tretinoin/adapalene — generally avoided (limited data; theoretical retinoid risk)

Safe options:

Adapalene 0.1% + BPO is safe and effective in adolescents ≥9 years

Isotretinoin: used in severe cases; concern about premature epiphyseal closure with prolonged courses — monitor growth

Doxycycline: avoid in children <8 years (tooth discoloration)

New-onset "acne" in elderly → consider rosacea, drug-induced acneiform eruption, or secondary malignancy (sebaceous carcinoma)

Complications of Acne and When to Escalate

Scarring:

Post-inflammatory hyperpigmentation (PIH):

Psychosocial complications:

Acne fulminans:

Board pearl: Acne fulminans can be precipitated by initiating isotretinoin at full dose → start low in severe disease.

Atrophic (ice-pick, rolling, boxcar) — most common

Hypertrophic/keloidal — more common on trunk, in darker skin

Presence of scarring at ANY severity level → escalate treatment aggressively

Scar treatment: chemical peels, microneedling, fractional laser resurfacing, subcision, fillers (post-acne)

Extremely common in skin of color

Managed with: topical retinoids, azelaic acid, vitamin C, chemical peels

Fades over months; sun protection is essential

Depression, anxiety, social isolation, ↓ self-esteem — screen actively

Severity of psychological impact does not always correlate with clinical severity

Explosive nodular acne + systemic symptoms (fever, myalgias, arthritis, ↑ ESR, leukocytosis)

Treatment: systemic corticosteroids first → then low-dose isotretinoin (starting isotretinoin alone can trigger flare)

Antibiotic Stewardship and Resistance Concerns

C. acnes resistance to antibiotics is rising globally → responsible prescribing is critical:

Principles:

If inadequate response after 3–4 months of oral antibiotics:

Gram-negative folliculitis:

Board pearl: A patient on long-term antibiotics for acne who develops a sudden pustular flare around the nose → think gram-negative folliculitis → isotretinoin is the definitive treatment.

Limit systemic antibiotics to ≤3–4 months

Always combine oral antibiotics with BPO to ↓ resistance

Never use topical antibiotic monotherapy

Do not combine topical and oral antibiotics of different classes

Use BPO-based regimens for maintenance (not antibiotics)

Do NOT rotate to another antibiotic indefinitely

Next best step: Escalate to isotretinoin (if severe/scarring) or add hormonal therapy (in women)

Complication of prolonged antibiotic use

Sudden flare of superficial pustules (perinasal) or deep nodules

Organisms: Klebsiella, Enterobacter, Proteus, E. coli

Treatment: isotretinoin (definitive) or appropriate gram-negative coverage

Key Differentials — Acneiform Eruptions

Rosacea:

Perioral (periorificial) dermatitis:

Drug-induced acneiform eruption:

Key distinction: Comedones (open/closed) are the hallmark of true acne vulgaris. Their absence suggests an acneiform mimic.

Central face (cheeks, nose, chin); papulopustules without comedones

Telangiectasias, flushing, ocular involvement

No comedones — this is the key distinction from acne vulgaris

Triggers: heat, alcohol, spicy food, sun

Treatment: topical metronidazole, azelaic acid, low-dose doxycycline (anti-inflammatory dose 40 mg MR)

Grouped papulopustules around mouth, nose, eyes; spares vermilion border

Often triggered by topical corticosteroids on face

Treatment: stop steroids, topical metronidazole or pimecrolimus; doxycycline if severe

Monomorphic papulopustules (uniform size), sudden onset

Culprits: corticosteroids (most common), EGFR inhibitors, lithium, phenytoin

Absence of comedones → key clue

Key Differentials — Folliculitis and Other Mimics

Bacterial folliculitis:

Pityrosporum (Malassezia) folliculitis:

Hidradenitis suppurativa (HS):

Folliculitis decalvans, dissecting cellulitis of scalp:

Board pearl: Pruritic + monomorphic + truncal + antibiotic-refractory = pityrosporum folliculitis until proven otherwise.

Staphylococcus aureus most common

Superficial pustules centered on hair follicles; may be pruritic

Can occur anywhere with terminal hair

Treatment: topical mupirocin; oral dicloxacillin or TMP-SMX if extensive

Pruritic, monomorphic papulopustules on trunk (chest, back, shoulders)

Often misdiagnosed as acne — fails to respond to antibiotics (may worsen)

Diagnosis: KOH prep shows yeast; biopsy shows follicular yeast spores

Treatment: topical ketoconazole; oral fluconazole or itraconazole if refractory

Recurrent painful nodules and abscesses in intertriginous areas (axillae, groin, inframammary)

Comedones may be present but distribution differs from acne

Sinus tracts and scarring are characteristic

Scalp involvement; scarring alopecia

Maintenance Therapy and Relapse Prevention

After achieving clearance:

Maintenance duration:

Post-isotretinoin:

General skincare counseling:

Board pearl: A topical retinoid is the cornerstone of both active treatment AND maintenance — never stop it prematurely.

Continue topical retinoid (adapalene or tretinoin) long-term — the single most important maintenance agent

Add BPO if needed for residual inflammatory lesions

Discontinue systemic antibiotics — do NOT use for maintenance

Indefinite in many patients; acne is chronic and relapsing

Particularly important in adult women and patients with scarring history

~80% achieve long-term remission after one course

~20% relapse → consider second course if severe; topical retinoid maintenance if mild relapse

Women with hormonal acne may relapse more frequently → spironolactone + COC for long-term control

Gentle, non-comedogenic cleanser twice daily

Non-comedogenic moisturizer (especially with retinoid use)

Daily broad-spectrum sunscreen (SPF ≥30) — retinoids ↑ photosensitivity

Avoid picking/squeezing lesions → worsens scarring and PIH

Monitoring Parameters During Treatment

Topical retinoids:

Oral antibiotics:

Isotretinoin monitoring schedule:

Spironolactone:

Board pearl: iPLEDGE mandates 2 forms of contraception (or abstinence) and monthly pregnancy tests throughout isotretinoin therapy and for 1 month after completion.

Expect initial irritation (dryness, peeling, erythema) — "retinoid dermatitis"

Temporary worsening in first 2–4 weeks ("purging") — counsel patients to persist

Reassess efficacy at 8–12 weeks (full effect takes time)

Reassess at 3 months → taper/discontinue if improved

Monitor for GI symptoms (doxycycline: esophagitis; minocycline: vestibular symptoms, pigmentation)

Baseline: 2 pregnancy tests (30 days apart), lipids, LFTs, CBC

Monthly: pregnancy test (must be negative to refill), lipids, LFTs

iPLEDGE program compliance: monthly online check-in for patient, prescriber, and pharmacy

Triglycerides >500 mg/dL → hold isotretinoin (pancreatitis risk)

LFTs >2× ULN → dose reduction or discontinuation

Baseline and periodic K⁺, renal function

Monitor for menstrual irregularities, breast tenderness

Ethical, Legal, and Patient Safety Considerations

iPLEDGE Program (isotretinoin):

Informed consent:

Psychosocial screening:

Board pearl: A patient requesting isotretinoin who refuses contraception or iPLEDGE enrollment cannot be prescribed the drug — no exceptions.

FDA-mandated REMS (Risk Evaluation and Mitigation Strategy)

Required for all patients, prescribers, and pharmacies

Female patients of reproductive potential: 2 negative pregnancy tests before start, monthly tests, 2 forms of contraception or documented abstinence

7-day prescription window (must pick up within 7 days of pregnancy test)

Male patients: also enrolled but no pregnancy testing

Discuss teratogenicity in clear terms — isotretinoin causes severe birth defects (craniofacial, cardiac, CNS)

Discuss mood changes — while evidence is inconclusive, screen for depression and suicidal ideation

Document blood donation restriction: cannot donate blood during and for 1 month after isotretinoin

Acne significantly impacts quality of life; validated tools (e.g., DLQI) can quantify burden

Lower threshold to treat aggressively when psychosocial impact is high, even if clinical severity appears mild

High-Yield Associations and Rapid-Fire Facts

Board pearl: Cheilitis during isotretinoin = expected; absence may suggest non-adherence.

Adapalene 0.1% = only OTC retinoid; best tolerated

Tazarotene = most potent topical retinoid; also category X

BPO = only topical that does NOT induce bacterial resistance

Doxycycline > minocycline for acne (safer, cheaper)

Isotretinoin → cheilitis in nearly 100% of patients (used as surrogate marker of compliance)

Isotretinoin + tetracycline = pseudotumor cerebri (contraindicated combination)

Isotretinoin + vitamin A supplementation = hypervitaminosis A (avoid)

Spironolactone → hyperkalemia risk; women only

COCs with anti-androgenic progestins (drospirenone, norgestimate) → preferred for hormonal acne

Acne excoriée → compulsive picking; treat underlying OCD/anxiety + acne

Neonatal acne = self-limited, no treatment usually needed

SAPHO syndrome: Synovitis, Acne, Pustulosis, Hyperostosis, Osteitis

Apert syndrome: severe acne + craniosynostosis + syndactyly (FGFR2 mutation)

Board Question Stem Patterns

16M, comedones + few papules on face → Mild acne → topical retinoid (adapalene) + BPO

17F, moderate papulopustular acne, failed topicals × 3 months → Add oral doxycycline; continue topical retinoid + BPO

19M, severe nodulocystic acne with scarring → Isotretinoin after baseline labs and iPLEDGE enrollment

22F, jawline acne, irregular menses, hirsutism → PCOS workup → COC + spironolactone + topical retinoid

Patient on isotretinoin, TG 650 → Hold isotretinoin; low-fat diet ± fibrate; recheck

15F on isotretinoin with new headache + papilledema → Pseudotumor cerebri → stop isotretinoin; check if on tetracycline

Pregnant woman with acne → Topical azelaic acid + BPO; avoid retinoids, tetracyclines

Patient on long-term doxycycline, sudden perinasal pustules → Gram-negative folliculitis → isotretinoin

Pruritic monomorphic truncal papulopustules, antibiotic-refractory → Pityrosporum folliculitis → antifungal therapy

30F, acne controlled on isotretinoin, asks about maintenance → Topical retinoid long-term after completing course

One-Line Recap

Acne vulgaris is a chronic inflammatory disorder of the pilosebaceous unit classified by lesion type and severity into mild (comedonal → topical retinoid ± BPO), moderate (papulopustular → add oral tetracycline for ≤3–4 months), and severe (nodulocystic/scarring → isotretinoin under iPLEDGE with strict pregnancy prevention and monthly lab monitoring), with hormonal therapy (COCs, spironolactone) as an adjunct in women, topical retinoids as the universal backbone for both treatment and maintenance, benzoyl peroxide as the key resistance-preventing agent always paired with antibiotics, and careful differentiation from mimics such as rosacea (no comedones), pityrosporum folliculitis (pruritic, monomorphic, truncal), and drug-induced acneiform eruptions.

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