An 11-year-old girl presents with warts on her fingers that have not responded to nonprescription wart medications (Figure 116-1). It causes her and her mother some social embarrassment and they would like to be rid of them. Her mother is also worried that it is affecting her daughter’s nails. The girl was able to tolerate the discomfort of liquid nitrogen treatment and wanted all her warts treated. The mother was instructed to purchase 40 percent salicylic acid to continue treatment of any residual warts at home.

Human papillomaviruses (HPVs) are DNA viruses that infect skin and mucous membranes. Infection is usually confined to the epidermis and does not result in disseminated systemic infection. The most common clinical manifestation of these viruses is warts (verrucae). There are more than 100 distinct HPV subtypes based on DNA testing. Some tend to infect specific body sites or types of epithelium. Some HPV types have a potential to cause malignant change but transformation is rare on keratinized skin.

Verrucae, verruca vulgaris, common warts.

• Nongenital cutaneous warts are widespread worldwide and are more common in children, with a peak incidence in the teenage years and a sharp decline thereafter.¹ Warts are the third most common reason for a pediatric general dermatology clinic visit accounting for about 16 percent of such visits.²

• They are most commonly caused by HPV types 1–5, 7, 27, and 29.¹

• Common warts account for approximately 70 percent of nongenital cutaneous warts.³

• Common warts occur most commonly in children and young adults (Figures 116-1 and 116-2).⁴

• Infection with HPV occurs by skin-to-skin contact. It starts with a break in the integrity of the epithelium caused by maceration or trauma that allows the virus to infect the basal layers.

• Warts may infect the skin on opposing digits causing “kissing warts” (Figure 116-3).

• Individuals with subclinical infection may serve as a reservoir for HPVs.

• An incubation period following inoculation lasts for approximately 2 to 6 months.

• Young age.

• Disruption to the normal epithelial barrier.

• More common among meat handlers.

• Atopic dermatitis.

• Nail biters more commonly have multiple periungual warts.

• Conditions that decrease cell-mediated immunity such as HIV (Figure 116-4) and immunosuppressant drugs.

Clinical Features

• The diagnosis of warts is based upon clinical appearance. Warts will obscure normal skin markings (Figure 116-5).

• Common warts are well-demarcated, rough, hard papules with irregular papillary surface. They are usually asymptomatic unless located on a pressure point.

• Warts may form cylindrical of filiform projections (Figures 116-6 and 116-7).

Typical Distribution

• Common anatomic locations include the dorsum of the hand, between the fingers, flexor surfaces, and adjacent to the nails (periungual; Figures 116-1, 116-2, and 116-5).