Wart

A wart (Latin verruca) is a common, possibly contagious, small, sharply circumscribed and usually benign epithelial growth of the upper skin layer (epidermis). Usually warts are slightly raised or flat. They are due to infection, usually with one of the more than 100 different "low-risk" human papillomaviruses from the Papillomaviridae family (non-enveloped, double-stranded DNA viruses). The infection occurs by contact infection or smear infection via the smallest injuries of the skin and mucous membranes. There, the viruses infect only the uppermost layer of the skin cells and multiply in their cell nuclei. Weeks to months can pass between the time of infection and the formation of warts. The particularly pronounced occurrence of warts on the entire body is referred to in medical terminology as generalized verrucosis.

The different forms of keratoderma as well as the fibroma pendulans (synonyms soft fibroma, fibroma molle, molluscum simplex), which is also called stalked wart or more correctly stalked fibroma, occur especially in the area of the neck and the upper eyelids and have no infectious cause.

Occurrence

Warts occur at any age and appear singly or in groups, usually as sharply defined, flat hemispherical or pointed outgrowths of the skin; rarely also completely flat, predominantly on the hands and feet. They are growths of the epidermis. The warts usually have a thick, horny, sometimes somewhat fissured coating of squamous epithelial cells, under which is soft, easily bleeding tissue of keratinocytes. Scratching warts can cause them to spread on the skin, as the bleeding that occurs and the infected skin cells it contains spread the viruses further along the body.

Despite their basically benign character, warts can cause considerable cosmetic disturbance, especially if they spread further on the skin, sometimes cause severe pain in certain areas and, extremely rarely, also develop malignantly (malignant).

Blood vessels as dark spots after callus ablation

Pathogen

An infection with the wart-causing human papillomaviruses or, only in the case of dell warts, with the molluscum contagiosum virus (MCV) does not generally take a serious course. There are exceptions in the case of considerably pre-damaged people, in the case of double or secondary infections (see also Infection). This shows that in the course of evolution these viruses and their reservoir host, humans, have adapted very strongly to each other.

Damage to its reservoir host is not a beneficial effect for a virus, as it is dependent on this host for its own reproduction. The symptoms nevertheless triggered in the reservoir host are side effects of the infection. Decisive for their severity is above all the state of the immune system of the affected person.

The role of the immune system

Also and especially in the case of infections with pathogens that are already adapted to humans as their reservoir host, the state of the immune system of the affected organism plays an important role. The observation that in the case of viral infections by no means all persons in contact also become ill has various causes. For example, immunity may already exist due to previous contact with this viral variant, the viral dose or virulence may be too low for an outbreak of disease, or the immune system may be able to prevent symptoms of disease despite infection (inapparent infection or silent celebration, i.e. immunisation without vaccination or disease). If the immune system is intact and the pathogen dose is low, warts may either not develop at all, take a less severe course or regress on their own after a few months without any treatment.

Since children's immune defenses are not yet as mature, they are also more frequently affected by warts. In the first four years of life, children statistically contract up to five bacterial or viral respiratory diseases. In this phase, there is also a higher risk of infection with the human papilloma virus type 1. However, in the case of painful warts in children, they should be treated particularly quickly so that the children do not adopt an evasive posture and cause a permanent malposition of the body due to the crooked appearance.

People with a weakened immune system, such as after a serious illness or in the case of immunosuppression, are also particularly at risk, and smokers also have an increased susceptibility to warts.

In the case of a severe disease of the immune system such as a rare idiopathic CD4 lymphopenia, it is possible for warts to spread all over the body (epidermodysplasia verruciformis). The case of the Indonesian fisherman Dede Koswara (the "tree man") has been reported in the media. After a subsequently diagnosed HPV-2 infection, in addition to more or less large warts on the entire body, increasingly horny structures proliferated over a period of years, especially on the hands and feet, which looked like tree bark.