Benign epidermal proliferations caused by human papillomavirus (HPV); morphology varies by anatomic site and HPV type.
Also known as: warts, verruca vulgaris, common wart, plantar wart, flat wart, condyloma acuminatum, genital warts, HPV
Overview
Benign epidermal proliferations caused by infection of keratinocytes by human papillomavirus (HPV). Clinical variants include common warts (verruca vulgaris), plantar warts (verruca plantaris), flat warts (verruca plana), filiform, periungual, and anogenital warts (condyloma acuminatum).
Epidemiology
Cutaneous warts affect ~10% of children and young adults. Genital HPV is the most common STI worldwide — ~80% lifetime prevalence in sexually active adults. Most infections clear spontaneously within 1-2 years.
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Question 1DermatologyEasy
A 9-year-old boy is seen for several common warts on his hands present for 8 months. He is otherwise healthy. Exam shows three hyperkeratotic papules on the dorsum of the right hand, one with surrounding skin maceration after a recent attempt at home cryotherapy. There is no fever, lymphadenopathy, or surrounding cellulitis. The lesions are otherwise typical verrucae vulgares. Which of the following is the most likely complication of these lesions?
AAutoinoculation and local spread
BPermanent loss of fingernail growth
CSystemic dissemination with viremia
DSquamous cell carcinoma
Reveal answer & full explanation
Correct answer: A — Autoinoculation and local spread
AAutoinoculation and local spread✓
BPermanent loss of fingernail growth
CSystemic dissemination with viremia
DSquamous cell carcinoma
Why autoinoculation and local spread is correct
Verruca vulgaris is a benign epidermal infection caused by cutaneous HPV strains, most often HPV 1, 2, and 4.
The great majority of lesions are self-limited and resolve over 1–2 years.
The most common clinically relevant complication is autoinoculation, in which virus is transferred by scratching, shaving, nail biting, or trauma to adjacent or distant skin, producing new lesions in a linear or clustered distribution.
Periungual and subungual spread is particularly common in nail biters; warts may also spread to family members via shared towels or shower floors.
Why the others are wrong
D) Squamous cell carcinoma — associated with high-risk mucosal HPV types (16, 18) in anogenital and oropharyngeal sites, not with cutaneous HPV 1/2/4 in common hand warts in immunocompetent children.
C) Systemic dissemination with viremia — does not occur because HPV replicates only in differentiating keratinocytes and never enters the bloodstream.
B) Permanent loss of fingernail growth — rare; periungual warts may temporarily distort the nail plate, but matrix destruction with permanent anonychia is not characteristic.
Question 2DermatologyMedium
A 12-year-old boy is brought to clinic for evaluation of bumps on his hands that have been present for 4 months. The lesions are asymptomatic but he is embarrassed about them at school. He denies trauma, fever, or systemic symptoms. Exam reveals several 3-6 mm firm, hyperkeratotic, skin-colored papules on the dorsa of both hands and one finger. Paring of the surface with a #15 blade reveals pinpoint black dots and small bleeding points; normal dermatoglyphic skin lines are interrupted over the lesions. Which of the following is the most likely diagnosis?
AMolluscum contagiosum
BSeborrheic keratosis
CVerruca vulgaris
DAcrochordon
Reveal answer & full explanation
Correct answer: C — Verruca vulgaris
AMolluscum contagiosum
BSeborrheic keratosis
CVerruca vulgaris✓
DAcrochordon
Why verruca vulgaris is correct
Verruca vulgaris (common wart) is a benign epidermal proliferation caused by human papillomavirus, most often HPV types 1, 2, and 4.
It is the most common viral skin infection in children and presents as firm, hyperkeratotic, skin-colored papules with a rough, cauliflower-like surface, most often on the hands, fingers, and knees.
Two classic clinical clues: interruption of the normal skin lines (dermatoglyphics) coursing over the lesion, and pinpoint black dots after paring, which represent thrombosed dermal capillaries within elongated dermal papillae.
Diagnosis is clinical; biopsy is rarely needed.
Why the others are wrong
A) Molluscum contagiosum — caused by a poxvirus; produces smooth, dome-shaped, pearly papules with central umbilication, not hyperkeratotic surfaces, and lacks black dots on paring.
B) Seborrheic keratosis — presents as a 'stuck-on,' waxy, sharply demarcated plaque most often in adults over 40 and is uncommon in children.
D) Acrochordon (skin tag) — a soft, pedunculated, flesh-colored papule found in skin folds such as the neck and axillae, not on the dorsal hands, and lacks hyperkeratosis.
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HPV infects basal keratinocytes through microabrasions; viral DNA replicates as keratinocytes differentiate. Productive infection produces hyperkeratosis, acanthosis, papillomatosis, and koilocytes (vacuolated cells with raisin-like nuclei). High-risk types integrate into host DNA, expressing E6/E7 oncoproteins that inactivate p53 and Rb → dysplasia and carcinoma over years to decades.
Periungual warts: around nail folds; nail biters; can cause nail dystrophy
Condyloma acuminatum (anogenital): pink to flesh-colored soft cauliflower-like papules and plaques on vulva, vagina, cervix, perianal area, penis, anal canal; can form large confluent masses (Buschke-Löwenstein tumor)
Bowenoid papulosis: pigmented well-demarcated papules on genitalia, SCC in situ histology
Classic findings
Verrucous papule with pinpoint black dots (thrombosed capillaries) that disrupts normal skin lines.
Differential diagnosis
Molluscum contagiosum — Smooth dome-shaped umbilicated papules; central core; poxvirus, not HPV
Seborrheic keratosis — 'Stuck-on' waxy plaques in older adults; not viral
Corn / callus (plantar wart DDx) — No skin lines disrupted, no thrombosed capillaries; paring reveals translucent keratin (vs black dots of wart)
Acrochordon (skin tag) — Pedunculated, neck/axilla, not verrucous surface
Anogenital warts (patient-applied): imiquimod 5% cream 3x/week × up to 16 weeks (immunomodulator); podofilox 0.5% solution/gel BID × 3 days then off × 4 days, up to 4 cycles; sinecatechins 15% ointment TID
HPV VACCINATION (PRIMARY PREVENTION): 9-valent HPV vaccine (Gardasil 9) — routinely at age 11-12 (can start at 9); catch-up through age 26; shared decision through age 45 (CDC ACIP)
Cervical cancer screening per USPSTF/ACOG: cytology q3y ages 21-29; cytology+HPV co-testing q5y OR cytology q3y OR primary HPV testing q5y ages 30-65
Recalcitrant cutaneous warts
Intralesional candida or mumps antigen immunotherapy
Intralesional bleomycin or 5-fluorouracil
Pulsed dye laser, CO2 laser
Topical cantharidin 0.7% in office (especially pediatric)
ACIP 2019 — Human Papillomavirus Vaccination for Adults: Updated Recommendations of the Advisory Committee on Immunization Practices (Meites et al., MMWR 2019)
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