Dr. Fox is a family physician in private practice in Defiance, Ohio, and editor for DynaMed (ww.dynamicmedical.com), a database of comprehensive updated summaries covering nearly 3,000 clinical topics. Dr. Brier is an editor for DynaMed.

Description
• Benign cutaneous papilloma (common wart)
• Single or grouped, rough keratotic papules, nodules, or plaques

ICD-9 codes  
• 078.10 viral warts, unspecified
• 078.19 other specified viral warts

Types
• “Common” warts (verruca vulgaris) are  single or grouped, rough keratotic papules, nodules, or plaques.
• Plane warts (verruca plana) are 2-4 mm in diameter, flat-topped with slight elevation and minimal scaling.
• Myrmecial warts have a deep “burrowing” quality.
• Mosaic warts are plantar or palmar warts (verrucae palmaris/verrucae plantaris) that coalesce into large plaques.
• Filiform warts have “frondlike” projections and occur most frequently on the face.
• Periungual warts occur along the nail margins, including proximal nail fold and hyponychium. 
• Condyloma acuminata are anogenital warts.


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Organs involved
• Skin and mucous membranes, most commonly on fingers, hands, knees, elbows, feet, and face

Prevalence
• Typically affects children and young adults (girls more frequently than boys)
• Estimated at 3.9%-5.3% in 6- to 16-year-olds.

Cause
• Human papillomavirus (HPV) invades epithelial cells with resultant cell proliferation and papule/nodule/plaque formation.
 
Transmission/risk factors
• Likely low rate of transmission to other people (estimated incidence <10%); however incubation period and duration of virus transmissibility are unknown
• Risk is higher with wet, macerated skin (e.g., communal shower use associated with increased risk of plantar warts).
• Auto-inoculation to secondary sites is common (scratching, shaving, etc.). 
• Nail biting and finger sucking can spread infection subungually and periungually.

Associated conditions
• Bowenoid papulosis (premalignant state)
• Squamous cell carcinoma (cervical and some anal, genital, and oropharyngeal cancers)
• Epidermodysplasia verruciformis (autosomal recessive disorder associated with chronic HPV infection)
• Heck’s disease (focal epithelial hyperplasia)

Presentation/diagnosis
• Skin growth, often correctly identified by the patient as a “wart”
• Lesions on the feet or near nails may be painful.
• Biopsy is generally unnecessary but may be appropriate for
    — Immunocompromised patients 
    — Lesions that are of uncertain etiology, resistant to treatment, suspicious for Bowenoid papulosis or squamous cell carcinoma 

D
ifferential diagnosis

• For common warts 
    — Molluscum contagiosum 
    — Nevus (mole) 
    — Seborrheic keratosis 
    — Skin tag 
    — Actinic keratosis 
    — Squamous cell carcinoma 
    — Linear epidermal nevus, inflammatory linear verrucous epidermal nevus 
• For plane warts 
    — Lichen planus 
    — Lichenoid keratosis
• For plantar wart (calluslike) 
    — Callus
    — Corn 
    — Talon noir (calcaneal petechiae) 

Prognosis
• Often self-limited (spontaneous clearance reported to be 80% within two years)
• Some lesions may grow in size and number over time.
• Lesions may become increasingly resistant to treatment over time.
• Immunosuppressed patients may
    — Have more numerous lesions 
    — Have higher treatment failure rates 
    — Be at increased risk of malignant transformation to squamous cell carcinoma.

Treatment
• May not be necessary because of self-limited nature of the disease
• Virtually all therapies have limited, firm (replicated) study data supporting them.
    — Cryotherapy commonly used  
    — Duct tape or moleskin 
    — Topical salicylic acid 
    — 5-Fluorouracil (5% cream) with occlusive dressing 
    — Photodynamic therapy with 5-aminolevulinic acid
    — Many other treatments that are used but supported only by limited or no clinical data  
         Topical imiquimod
         Retinoids
         Cantharidin
         Bichloroacetic acid
         Dinitrochlorobenzene solution
         Silver nitrate solution
         a-Lactalbumin plus oleic acid
         Formic acid
         Zinc
         Diphencyprone (diphenylcyclopropenone)
         Ciclopirox-containing lacquer
         Intralesional injection of skin test antigens
         Bleomycin
         Combination of 5-fluorouracil, lidocaine, and epinephrine 
         Laser treatment 
         Oral zinc sulfate, cimetidine, levamisole  
         Hypnotic and “suggestion” therapies, including use of “wart tape” 

Prevention
• Avoid barefoot use of communal showers.
• Refrain from scratching or shaving lesions.
• No need for children to be excluded from attending  school or participating in sports

For complete references, see www.dynamicmedical.com.