Chapter 137: Common Warts

PATIENT STORY

An 11-year-old girl presents with multiple warts on the fingertips that have been present for 3 months (Figure 137-1). She occasionally bites at the warts. Mom has tried over-the-counter freezing, but it was very uncomfortable for her daughter. Although the family is anxious about them spreading, you recommend watchful waiting, and in 6 months all warts have completely resolved.

INTRODUCTION

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 200 distinct HPV subtypes based on DNA testing. Some tend to infect specific body sites or types of epithelium. Some types have potential to cause malignant change, but this is rare on keratinized skin.

SYNONYMS

Verrucae, verruca vulgaris, common warts.

EPIDEMIOLOGY

• 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

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

• High-risk HPV has been isolated in warts but the significance is unclear.²

• Common warts account for approximately 70% of non-genital cutaneous warts.³

• Common warts occur most commonly in children and young adults (Figures 137-1 and 137-2).⁴

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 137-3).

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

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

RISK FACTORS

• Young age¹.

• Disruption to the normal epithelial barrier.

• More common among meat handlers.⁵

• Atopic dermatitis.

• Nail biters more commonly have multiple periungual warts.

• Conditions that decrease cell-mediated immunity such as HIV (Figure 137-4) and immunosuppressant drugs (...