Warts and Molluscum Contagiosum

1

What causes warts?

Warts are caused by the human papillomavirus (HPV), a nonenveloped double-stranded DNA virus. There are over 200 known HPV types, and over 100 have been totally sequenced. The virus infects basal keratinocytes, resulting in keratinocyte hyperproliferation.

2

Do any warts come from toads?

No. There is no supportive scientific evidence—histologic, viral, or other—that the bumps on the skin of a toad are at all related to warts.

3

Name the common types of warts.

HPV infection is highly specific for the epithelia of the skin or mucosa. Some HPV types are associated with specific clinical presentations ( Table 26.1 ). For example, flat warts are seen primarily on the face and hands of both children and immunosuppressed patients and are often caused by HPV-3 and -10 ( Fig. 26.1 A ). Common warts occur most often on the fingers, elbows, and knees and are frequently associated with HPV-1, -2, and -4 ( Fig. 26.1 B). An example of warts in an immunosuppressed patient can be seen in Fig. 26.1 C.

4

How are warts transmitted?

HPV is primarily transmitted via direct skin-to-skin contact with an infected individual and less frequently through fomites. Genital warts are most commonly transmitted through sexual intercourse. HPV may also be aerosolized during laser and electrocautery procedures leading to respiratory papillomatosis, which highlights the importance of wearing appropriate safety masks during these procedures. Any skin disease (i.e., atopic dermatitis) that affects the integrity of the stratum corneum may be associated with an increased risk of acquiring HPV infection. External factors may also affect barrier function. Warts can be acquired at swimming pools, where rough concrete surfaces may abrade the skin. Warts on hair-bearing skin may be spread by shaving. Periungual warts are often found in persons who have a habit of biting their cuticles.

5

How long is the incubation period of warts?

Unknown. It is estimated to be several weeks to months. HPV is demonstrable by DNA hybridization and polymerase chain reaction in skin that is clinically normal, indicating the likelihood of a latent or subclinical form of HPV. In addition, it is not uncommon for a wart to recur in the same location many years following apparent resolution.

6

Are some people more susceptible to warts than others?

Warts are common in healthy children and young adults; however, individuals with compromised cell-mediated immunity are more susceptible to warts than others. This includes patients with certain blood cell cancers, HIV infection, a primary immunodeficiency syndrome, or transplant patients on immunosuppressive drugs. Diseases that affect the barrier function of the skin also increase susceptibility to warts.

7

What is epidermodysplasia verruciformis (EV)?

EV is a rare, inherited disorder in which cutaneous HPV infection is generalized and persistent. Most cases are autosomal recessive, but autosomal dominant and X-linked dominant forms are also reported. It is caused by mutations in either the EVER1 or EVER2 genes located on chromosome 17. The lesions are either flat warts or reddish-brown plaques, often developing in sun-exposed areas ( Fig. 26.2 A ). Actinic keratosis begins to develop after the age of 30, and approximately half of EV patients will develop squamous cell carcinoma (SCC). HPV types 5 and 8 are associated with EV.

Przybyszewska J, Zlotogorski A, Ramot Y. Re-evaluation of epidermodysplasia verruciformis: reconciling more than 90 years of debate. J Am Acad Dermatol. 2017;76:1161–1175.