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Patient Story

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.

FIGURE 116-1

Common warts on the fingers of an 11-year-old girl. These periungual warts are particularly difficult to eradicate. (Used with permission from Richard P. Usatine, MD.)


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

FIGURE 116-2

Common warts on the hand of a 9-year-old boy. (Used with permission from Richard P. Usatine, MD.)

Etiology and Pathophysiology

  • 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.

FIGURE 116-3

Warts may infect the skin on opposing digits causing “kissing warts.” (Used with permission from Richard P. Usatine, MD.)

Risk Factors1...

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