Warts comprise a heterogeneous group of lesions that are all due to excessive proliferation of skin and mucosal skin cells. They are actually a viral infection of epidermal cells by different types or strains of the human papillomavirus (HPV). Virtually any part of the skin may be infected by HPV and manifest with warts, but warts most commonly affect the face and neck, torso and extremities. Warts involving the genitals and anal region are considered as sexually transmitted infections, and, if caused by particular types of HPV (specifically HPV 16 and 18), may actually predispose to squamous cell carcinoma. While all warts involve hyperproliferation of the skin and mucosa, there are a wide variety of physical manifestations of warts.
Also termed verruca vulgaris, common warts appear as bumps or elevated lesions in the skin having a rough and irregular surface. Common warts range in size from barely noticeable 1 mm bumps to obvious lesions larger than 1 cm. Common warts are typically completely asymptomatic or slightly itchy and can appear on any part of the body.
Some warts appear as long and slender growths, similar to skin tags, which can be seen in the face and neck. These are called filiform warts, which are also called facial warts.
Warts may also be found in weight-bearing areas, such as the ball and head of the feet or in the palms, usually around the area of the fingertips and nails. These deep palmoplantar warts, also called myrmecia, are sharply defined round lesions with rough surfaces and often surrounded by a collar of calloused skin. Since myrmecia can invade deep into the skin, they can be painful.
Flat or slightly elevated warts are named plane warts or verruca plana. In contrast to verruca vulgaris, flat warts often have smooth surfaces. These kinds of warts may occur anywhere in the body, but usually affect the face, hands and shins.
Butcher’s warts appear very similar to common warts. However, as their name implies, this kind of warts is most often found in the hands that frequently handle raw meats.
When multiple warts are located very close to each other, they may compress very tightly to form a single raised and flat lesion called a mosaic wart.
Warts that involve either the male or female genitalia are termed genital warts or condyloma acuminata. Typical lesions are cauliflower-like growths surrounding the glans penis or hyperkeratotic lesions of the shaft. Genital warts are also often found in the labia or, rarely, also in the vagina.
Also termed focal epithelial hyperplasia, Heck’s disease is characterized by multiple flat-topped or dome-shaped pinkish bumps in the mucosa of the lower lip, cheeks, gums or tongue.
Some warts in the weight-bearing areas of the sole appear as smooth cystic nodules with a white cheesy material inside. These are cystic warts, which are theorized to originate from the epidermis infected with HPV that subsequently become implanted in the dermis to form an epidermal inclusion cyst.