Cause
Warts are caused by the human papilloma virus (HPV). There are about 130 known types of human papilloma viruses. HPV infects the squamous epithelium, usually of the skin or genitals, but each HPV type is typically only able to infect a few specific areas on the body. Many HPV types can produce a benign growth, often called a "wart" or "papilloma", in the area they infect. Many of the more common HPV and wart types are as follows:
- Common warts - HPV types 2 and 4 (most common); also types 1, 3, 26, 29, and 57 and others.
- Cancers and genital dysplasia - "high-risk" HPV types are associated with cancers, (cervical cancer and can also cause some vulvar, vaginal, penile, anal and some oropharyngeal cancers. "low-risk" types are associated with warts or other conditions.)
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- High-risk: 16, 18 (cause the most cervical cancer); also 58, 33, 45, 31, 52, 35, 39, 59, and others.
- Plantar warts (myrmecia) - HPV type 1 (most common); also types 2, 3, 4, 27, 28, and 58 and others.
- Anogenital warts (condylomata acuminata or venereal warts) - HPV types 6 and 11 (most common); also types 42, 44 and others.
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- Low-risk: 6, 11 (most common); also 13, 44, 40, 43, 42, 54, 61, 72, 81, 89, and others.
- Flat warts - HPV types 3, 10, and 28.
- Butcher's warts - HPV type 7.
- Heck's disease (Focal epithelial hyperplasia) - HPV types 13 and 32.
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