What are Warts?

Warts are so common that maybe you’d think the question isn’t worth asking, but the answer might surprise you.  We actually know a lot about warts.  The common wart, or Verruca vulgaris, is a common, benign skin growth caused by a viral infection in the skin.  The virus is human papilloma virus (HPV), which is a double-stranded, DNA virus.  The viruses infect keratinocytes, which are found in the skin, as well as the mouth and throat, vagina, cervix, and rectum.  Most infections are harmless and resolve within 1-2 years.  However, there are over 100 different types of HPV, referred to by numbers, and some of them have the potential to cause cancer.  They do this by producing two viral proteins called E6 and E7 that interfere with the human p53 and pRb proteins, which are key in cancer development.

Who gets Warts?

Probably everybody.  Some studies have estimated that 90% of American have a wart infection at some point in their life.  Most of the studies focus on genital warts and show that about 75% of sexually active Americans will be infected with HPV at some point in their lifetime.  It is believed that there are 6 million new cases of HPV infections each year in Americans between 15 and 44 years old, with 75% of these in the 15-24 year old age group.

Types of Warts caused by Human Papilloma Virus (HPV)

Some of the subtypes of HPV like to infect certain parts of the body or have other associations, as shown here:

Common warts (2 and 4)

Flat warts (3, 8, and 10)

Oral papilomas (6, 7, 11, 16, 32)

Butcher’s warts (7)

Low risk genital warts (6 and 11)

High risk genital warts (16 and 18)

Plantar’s warts (1, 2, 4, or 63)

Carcinogenic  1(6, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 68, 73, and 82)

Cutaneous Warts

Warts on the skin are the most common.  Cutaneous warts can be broken down into subtypes including planters warts on the feet, flat warts which remain flat, filiform warts which tend to have little spires that stick out, periungual warts on the fingers and toes around the nails, and butcher’s warts which are seen mostly on the hands of butchers.  These warts are very common in early childhood and usually resolve.  They occur most commonly on the hands, elbows, and knees.  If children with warts on their hands bite their nails, they sometimes develop warts around their mouth.

How are cutaneous Warts spread?

Direct contact and shared objects.

Should I be worried about cutaneous Warts causing cancer?

Warts in children are almost never associated with cancer.  In older adults, HPV is now being identified in more and more squamous cell carcinomas and may be an important factor in these tumors.

Genital Warts

Genital warts refers to warts occurring in the vagina, cervix, penis, scrotum, and/or ano-rectal area.  They are sexually transmitted.  The vast majority of genital HPV infections do not cause any symptoms.  In a few months, our immune system usually recognizes the infection and clears it.  This seems to lead to immunity to that particular strain of HPV.

Genital Warts and Cancer

The main problem with genital warts is that some people don’t really clear the infections well and end up with a smoldering infection.  Some strains of HPV, known as the high risk types 16, 18, 31, and 45, can lead to cancer.  HPV 16 causes about 50% of all cervical cancer and an even greater percentage of vaginal and vulvar cancers.  It has also been found in penile cancer (very, very rare), anal cancers, and head and neck cancers.  It is possible to test genital warts to determine if they are a high or a low risk subtype.

The vaccines Gardisil and Cervarix target HPV viruses.  Both protect against HPV 16 and 18, which cause most cervical cancers, but Gardisil adds protection against 6 and 11, which cause about 90% of genital warts.  Since the prevention of cancer, in particular by a vaccine, has been on of the holy grails of modern medicine, these vaccines will be memorialized in history as being the first widely distributed vaccine that does this.  Gardisil is recommended for both girls and boys in the United States. Importantly, the vaccine is likely to be ineffective once infection has occurred, so it is important that it be given prior to sexual activity in order for it to make a dent in the 4,000 deaths from cervical cancer each year.

Gardisil is also now recommended for teenage boys.  Initially, this was recommended as a way to reduce the amount of HPV in the country and protect women.  Certainly, given the stigma of sexually transmitted diseases, having immunity to this infection probably ought to be welcomed as well.

Recently, it has been found that the rates of oral or throat cancer are rising fast, with a rate that has nearly quadrupled in the last 16 years.  HPV 16 is now being found in many of these cancers, and presumably got there through oral sex.  It hasn’t been proven that Gardisil will prevent this cancer, but the CDC believes it will and has made this part of the rationale for vaccinating boys as well as girls.

The vaccine is expensive, about $360, but it is covered through the federal vaccines for children program.  These cancers, vaginal cancer, cervical cancer, rectal cancer, penile cancer, and oral cancer are not terribly uncommon, but their treatment with surgery, radiation, and chemotherapy is anything but easy.

Treatments for Warts

There are a very large number of treatments available for warts, partly because no single treatment is 100% effective.

Wart Destruction

One option is to destroy warts by cutting, burning, or freezing them away.  Depending on the size, number, and location of warts, this is often a very quick and cost-effective approach.

Beetlejuice for Warts

Cantharidin is one of the most effective and easy to use treatments for warts.  It is referred to as beetlejuice because it was originally obtained from a blistering beetle.  When applied to a wart, it causes a blister to form which usually removes the wart in 1-2 treatments without leaving a scar.  Unfortunately, cantharidin has not received FDA approval because it is a generic product and there really is no money it for any company to go through clinical trials.  It is therefore used on an off-label basis.  However, it has been used safely in this country for over 50 years and is widely used worldwide.

Topical medicines to treat Warts

Imiquimod is an immune stimulating cream that may be applied three times a week to warts for 8-12 weeks. It works by stimulating a local immune reaction that leads to destruction of the warts.

Veregen is a botanical drug, derived from green tea, and is actually the first FDA approved botanical drug in the United States.  It is applied three times a day for 8-12 weeks.

Podofilox is a topical irritant that is applied to warts to also try to induce an immune reaction.

Other treatments for Warts

When nothing else works, warts can be injected to destroy them

Candin is protein derived from candida yeast that can be injected into warts to stimulate an immune response.  It has now become our favored treatment for warts because of its very high overall success rate