What causes plantar warts on the feet in adolescents?

From the Guidelines

Plantar warts on the feet in adolescents are caused by infection of keratinocytes by human papillomavirus (HPV).

Key Points

• The development of epidermal thickening and hyperkeratinization occurs following infection at the basal layer and clonal proliferation, which eventually results in a visible wart, weeks or even months later 1.
• HPV can spread from one individual to another by direct contact or via the environment, and it is not known exactly how long the infectious virus can persist outside the body 1.
• The majority of common warts, including plantar warts, are caused by HPV types 1,2,4,27 or 57 1.
• Some key characteristics of plantar warts include:
  • Located on the sole of the foot
  • Can be distinguished from other keratotic lesions on the feet, such as actinic keratoses, knuckle pads or, more rarely, squamous cell carcinoma or focal palmoplantar keratoderma, by paring down the wart and observing pinpoint bleeding as the capillary loops of the elongated dermal papillae are exposed 1.

Epidemiology

• Infection is common in childhood, but can occur at any age, with small cohort observational studies suggesting that 5–30% of children and young adults have warts 1.
• Spontaneous clearance of the infection can occur at any time from a few months to years later, with half of warts in children clearing at 1 year and about two-thirds by 2 years 1.

From the Research

Causes of Plantar Warts

• Plantar warts are caused by infection with the human papillomavirus (HPV) 2, 3, 4, 5, 6
• The virus can infect the skin through small cuts or abrasions, and can be spread through contact with contaminated surfaces or other people 5, 6

Risk Factors

• Adolescents are at higher risk of developing plantar warts due to their increased exposure to HPV in public places such as locker rooms and shower rooms 3
• Using communal showers can increase the risk of developing plantar warts, with one study finding a statistically significant difference in prevalence between shower room users and those who only used locker rooms 3
• Certain subtypes of HPV, such as HPV 2, HPV 27, HPV 57, and HPV 63, are more commonly found in pediatric populations and can increase the risk of developing plantar warts 4

Transmission

• Plantar warts can shed HPV, which can then infect other sites on the foot or spread to other people 5
• The virus can be spread through contact with contaminated surfaces or other people, making it difficult to control the spread of infection 5