Aetiology
Common warts are caused by human papillomavirus (HPV) infection of keratinocytes. HPV infection may be clinical, sub-clinical, or latent. Common warts are most frequently caused by HPV types 1, 2, 4, 27, 57, and 63, but other HPV types may also be involved in the pathogenesis.[1][2] Plantar warts are usually associated with HPV-1. Butcher warts are due to repetitive trauma to the hands, and are classically associated with HPV type 7, but can also be caused by HPV types 2, 4, and 27.
Certain factors seem to contribute to the risk of developing common warts. Water immersion (e.g., swimming or regular dishwashing) is a risk factor. Similarly, any skin condition causing breaks in the skin will increase the risk of acquiring warts in the area, if physical contact with a wart occurs. The prevalence of warts is 50% in people whose occupation involves direct handling of meat or fish. People who bite their nails have an increased risk of developing periungual warts.[1][2] Immunocompromised patients are more susceptible and tend to have more lesions, and occasionally increased lesion size and different morphology, compared with immunocompetent individuals.
Pathophysiology
Human papillomavirus infection of keratinocytes causes koilocytosis (viral transformation of the keratinocyte) and proliferation.[2]
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