Verruca vulgaris (wart)
This is a well – localized horny projection that is common on the fingers, hands, feet and knees, particularly of children and young adults. Crops of warts may occur on the genitalia and perianal region, in many cases spread by sexual contact. Warts are often multiple and are due to a number of different strains of human papilloma virus.
Warts are due to infection by the human papillomavirus (HPV), a double-stranded DNA virus. There are more than 150 known HPV types, only some of which infect the skin, giving rise to a variety of clinical presentations. Infection begins in the basal layer of the epidermis, causing proliferation of the keratinocytes (skin cells) and hyperkeratosis, and production of infectious virus particles — the wart. The most common HPV types infecting the skin are types 1, 2, 3, 4, 10, 27, 29, and 57.
HPV is spread by direct skin-to-skin contact or autoinoculation; if a wart is scratched or picked, a wart may develop under the fingernail (subungual wart) or virus may be spread to another area of skin. Autoinoculation of the virus in a scratch can result in a line of warts (pseudo-koebnerisation) The incubation period can be as long as twelve months, depending on the amount of virus inoculated.
Microscopically, there is a local hyperplasia of the prickle cell layer of the skin (acanthosis) with marked surface cornification.
Untreated, warts usually vanish spontaneously within 2 years, hence the apparent effi cacy of folklore ‘wart cures’. Often, reassurance that these lesions will disappear is all that is required, but if treatment is demanded they can be burnt down by the application of a silver nitrate stick or podophyllin, frozen with liquid nitrogen, or curetted under local or general anaesthesia.