PLANTAR WARTS

Overview

Plantar warts are benign (noncancerous) growths that occur on the sole (plantar surface), heel, or ball of the foot. Pressure from standing and walking often causes them to grow into deep layers of the skin.

The human papilloma virus (HPV) causes several different types of warts, which are the most common type of skin infection. In some cases, the HPV virus dies within 1 or 2 years, and warts simply disappear. Podiatrists may recommend having plantar warts removed because they often are irritating and painful.

Incidence and Prevalence

Anyone can contract the virus that causes plantar warts. According to the American Podiatric Medical Association (APMA), plantar warts occur most often in children and young adults between the ages of 12 and 16. Incidence is higher in people who share common bathing areas (e.g., dormitory students, gym members).

Cause and Risk Factors

Plantar warts can occur when HPV invades the body through tiny cuts or breaks in the skin on the bottom of the feet. The virus often is encountered on contaminated surfaces, such as the tile floors of public locker rooms, showers, and swimming pools. Normally, antibodies in the blood destroy HPV, but in some cases, it takes refuge in the skin and causes plantar warts.

Some people are more prone to the virus that causes plantar warts than other people. Risk factors include repeated HPV exposure (e.g., walking barefoot in public locker rooms and common bathing areas) and having a weakened immune system. In some cases, the virus can be transmitted to the feet from other areas of the body (called remote location seeding).

Signs and Symptoms

Plantar warts usually are rough and spongy, and most are gray, brown, or yellow with dark pinpoints (tiny capillaries that supply blood to the wart). Scraping a wart may cause it to bleed.

A plantar wart is similar in structure to an iceberg-the part on the surface of the skin is a small part of the entire anomaly. Often, the portion of the wart under the skin is at least twice as big as the part you can see.

Plantar warts may cause pain on the bottom of the foot. Patients often feel a "lump" on the bottom of the foot when standing, similar to having a stone in the shoe. In many cases, pressure from standing and walking prevents plantar warts from rising above the skin surface.

If left untreated, plantar warts can grow up to 1 inch in circumference and may spread into clusters (called mosaic warts). In severe cases, they cause a change in gait or posture that results in leg or back pain.

Diagnosis

Most plantar warts are diagnosed based on their appearance. In some cases, the podiatrist scrapes a sample of skin cells from the wart and sends the sample to a pathologist for microscopic evaluation.

Treatment

Over-the-counter medications contain chemicals that destroy skin cells (e.g., acid) and may damage healthy tissue surrounding the wart and contribute to spreading. Self-treatment for plantar warts using an over-the-counter preparation is not recommended.

In some cases, podiatrists apply mild acid (e.g., salicylic acid, cantharidin, dichloroacetic acid) topically to treat plantar warts. This treatment, which often requires multiple applications over the course of several weeks, disintegrates viral cells and allows healthy skin cells to replace them.

Prevention

According to the American Podiatric Medical Association (APMA), the following may help to prevent plantar warts:

• Avoid walking barefoot whenever possible.
• Change shoes and socks daily.
• Keep feet clean and dry.
• Check children's feet periodically.
• Avoid direct contact with warts on other persons or on other parts of the body.
• Do not ignore growths on, or changes in, your skin.
• Visit a podiatrist as part of your annual health checkup

Questions to Ask Your Doctor about Plantar Warts

• How might I have come in contact with the human papillomavirus?
• How does HPV cause plantar warts?
• Might I have transferred the virus to my foot from another part of my body?
• Does HPV stay in the body for a long time? If so, is that harmful?
• Will a sample of cells from the wart be removed for a pathologist to analyze?
• If so, what does this procedure involve?
• Who will explain the test results to me?
  Telephone number to call:
• What types of treatment options are available?
• Might my plantar warts go away without treatment?
• Do you recommend treatment? Why or why not?
• What kind of treatment do you recommend?
• What are the benefits, risks, and side effects of this treatment?
• Why shouldn't I use an over-the-counter medication to self-treat my plantar warts?
• Might acid applications be helpful?
• If so, what does this treatment involve and how frequently will I need these applications?
• If acid applications are used, how long does it usually take for plantar warts to go away?
• What do laser treatment procedures, cryotherapy, and curettage involve? Might these treatments be helpful?
• Are these procedures painful?
• What can I expect after undergoing these treatments?
• Will I be able to walk normally?
  Restrictions:
• What are my options if none of these treatments is successful?
• How often should I follow up with a podiatrist after treatment?
• How can I prevent contracting plantar warts in the future?
• What kind of shoes do you recommend to protect my feet and avoid HPV infection?

Do open shoes, such as flip-flops or sandals, increase my risk for developing plantar warts?

• When I check my feet or my children's feet for plantar warts, what should I look for?
• How can I learn more about plantar warts?