Chapter 6: Infections and Infestations
Viral Infections: Verrucae (Warts)
What causes them?
Verrucae (warts) are a common condition caused by human papilloma virus (HPV). There are many sub-types of HPV, and each is most commonly seen in a characteristic location on the skin. Warts can occur anywhere on the skin, from the thick skin on the soles of the feet to the mucosal skin of the lips and genitals. Most warts are little more than an annoyance, but others can be associated with cancer formation.
There are 4 basic types of warts:
- Verruca Vulgaris (common warts) – Usually seen on the backs of the hands or around fingernails but can be anywhere. Very common in children. Raised, rough-surfaced lesions. May be single or in a cluster.
- Verruca Plana (flat warts) – Most common on face, neck, arms, and legs. Often seen in a straight line where skin was scratched (Koebnerization). Smooth, flat-topped papules often seen in clusters. People may have hundreds in one area.
- Verruca Plantaris (plantar warts) – Appear on the bottom of the feet. Often grow inward and more deeply than other warts. Most symptomatic of all warts due to pressure when standing. May lead to altered gait in children.
- Condyloma Acuminata (genital warts) – Seen around the anogenital track. Skin coloured, soft papules from 1-5 mm. Some subtypes are associated with cancer, especially cervical cancer. In very young children, spread is usually incidental, but in children between ages 5-12, the possibility of spread through sexual abuse should be considered.
How does someone get them?
Warts are passed from person to person. Usually this occurs by skin contact, especially if the person had a small cut or scrape in the area to allow viral penetration. Individuals with decreased immune function due to cancer or HIV can have a large number of warts.
How are they treated?
There is no specific anti-viral therapy for HPV. Warts that are not bothersome to the patient can be watched in the hope that the patient’s own immune system will recognize and clear the wart virus. Most therapies work by causing irritation, which increases the speed of this recognition by the patient’s own immune system. There are many different treatments available for warts and each requires diligence.
- Over-the-counter salicylic acid preparations must be applied daily and work best when occluded with tape or a bandage unless the medication is formulated into an acrylic.
- Duct tape occlusion for five days before changing has also been shown to be effective. When it is removed, the wart is softened by soaking and then worn down with a nail file or pumice stone before a new piece of tape is applied.
- Topical retinoids such as tretinoin can be useful for flat warts
- Topical imiquimod or sinecatecinins can be used for condylomata acuminata
- Liquid nitrogen (cryotherapy) is the mainstay of therapy where it is available, but this treatment is painful and requires multiple visits and applications.
- Paring with a 15 blade scalpel decreases the pain of walking on plantar warts and can be followed by application of silver nitrate, which may leave a stain on the skin, but is an effective therapy.
- Canthardin can be applied in office, but increases risk of ring wart (central clearance with peripheral spread of wart) development. It should be washed off in 2-4 hours after application and should not be prescribed for home application.
In many places, HPV vaccine is given to males and females in young adolescents as part of the routine immunization program. This vaccine covers 9 strains of HPV, which cause ~90% of cervical cancers and the majority of anogenital warts. It is also indicated for other at-risk populations who may not have received it as part of the routine immunization program.
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