|verruca, myrmecia, verruca plantaris:405|
Large plantar wart
|Classification and external resources|
Plantar warts are usually self-limiting, but treatment is generally recommended to lessen symptoms (which may include pain), decrease duration, and reduce transmission. Infection occurs in an estimated 7–10% of the US population, and genetics plays an important role in determining susceptibility.
Plantar warts are benign epithelial tumors generally caused by infection by human papilloma virus types 1, 2, 4, 60, or 63, but have also been caused by types 57, 65, 66, and 156. These types are classified as clinical (visible symptoms). The virus attacks compromised skin through direct contact, entering through possibly tiny cuts and abrasions in the stratum corneum (outermost layer of skin). After infection, warts may not become visible for several weeks or months. Because of pressure on the sole of the foot or finger, the wart is pushed inward and a layer of hard skin may form over the wart. A plantar wart can be painful if left untreated.
A plantar wart is a small lesion that appears on the surface of the skin and typically resembles a cauliflower, with tiny black petechiae (tiny hemorrhages under the skin) in the center. Pinpoint bleeding may occur when these are scratched. Plantar warts occur on the soles of feet and toes. They may be painful when standing or walking.
Plantar warts are often similar to calluses or corns, but can be differentiated by close observation of skin striations. Feet are covered in skin striae, which are akin to fingerprints on the feet. Skin striae go around plantar warts; if the lesion is not a plantar wart, the striations continue across the top layer of the skin. Plantar warts tend to be painful on application of pressure from either side of the lesion rather than direct pressure, unlike calluses (which tend to be painful on direct pressure instead).
HPV is spread by direct and indirect contact from an infected host. Avoiding direct contact with infected surfaces such as communal changing rooms and shower floors and benches, avoiding sharing of shoes and socks and avoiding contact with warts on other parts of the body and on the bodies of others may help reduce the spread of infection. Infection is less common among adults than children.
As all warts are contagious, precautions should be taken to avoid spreading them. The British National Health Service recommends that children with warts:
- cover them with an adhesive bandage while swimming
- wear flip-flops when using communal showers
- should not share towels.
Plantar warts are not prevented by inoculation with currently available HPV vaccines because the warts are caused by different strains of the human papillomavirus. Gardasil protects against strains 6, 11, 16, and 18, and Cervarix protects against 16 and 18, whereas plantar warts are caused by strains 1, 2, 4, and 63.
|First-line therapy||Over the counter salicylic acid|
|Second-line therapy||Cryosurgery, intralesional immunotherapy, or pulsed dye laser therapy|
|Third-line therapy||Bleomycin, surgical excision|
Treatments that have been found to be effective include:
Salicylic acid — The treatment of warts by keratolysis involves the peeling away of dead surface skin cells with keratolytic chemicals such as salicylic acid or trichloroacetic acid. These are available in over-the-counter products or, in higher concentrations, may need to be prescribed by a physician. A 12-week daily treatment with salicylic acid has been shown to lead to a complete clearance of warts in 10–15% of the cases.
Immunotherapy — Intralesional injection of antigens (mumps, candida or trichophytin antigens USP) is a new wart treatment which may trigger a host immune response to the wart virus, resulting in wart resolution. It is now recommended as a second-line therapy.
Liquid nitrogen — This, and similar cryosurgery methods, is a common surgical treatment which act by freezing the external cell structure of the warts, destroying the live tissue. Up to three sessions may be required.
Electrodesiccation and surgical excision, which may produce scarring.
Microwave ablation — This is a new treatment that uses microwave induced heat to destroy the virus. This technique is more effective than cryosurgery or salicylic acid and less painful than laser with low risk of scars.
Cauterization — This may be effective as a prolonged treatment. As a short-term treatment, cauterization of the base with anaesthetic can be effective, but this method risks scars or keloids. Subsequent surgical removal is unnecessary, and risks keloids and recurrence in the operative scar.
A 2006 review looked at sixty trials on the effects of different "local treatments for surface, non-genital warts in healthy people", (i.e. not looking specifically at plantar warts).
The review concluded: 
- there is a lack of good evidence because many trials had poor methodology
- the average cure rate using a placebo was 27% after an average period of 15 weeks.
- treatments containing salicylic acid are "clearly better than placebo"
- two trials comparing salicylic acid and cryotherapy showed no significant difference in efficacy.
A 2010 study compared the efficacy of cryotherapy versus topical salicylic acid versus "wait and see" in the treatment both of cutaneous and plantar warts. After a randomized controlled trial over a treatment period of 13 weeks, with a sample size of 250 participants the study concluded that:
- Regardless of treatment, children with plantar warts showed relatively high cure rates (about 50%), whereas plantar warts in adolescents and adults were highly persistent (cure rates of about 5%).
- For plantar warts, we found no clinically relevant difference in effectiveness between cryotherapy, topical application of salicylic acid or a wait-and-see approach after 13 weeks.
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