Differential Diagnoses:
Seborrheic keratosis
Actinic keratosis
Corns
Squamous cell carcinoma
Diagnosis: Verruca vulgaris
Learnings: Common warts (verruca vulgaris) are benign skin proliferations caused by infection of the epidermis with human papillomavirus (HPV), most frequently types 1, 2, and 4. Verruca vulgaris lesions may be acquired from direct contact with HPV-infected skin or, less commonly, from contact with HPV-carrying fomites. Autoinoculation is very common. Warts are frequent at locations that are traumatized. HPV types 2 and 4 may infect virtually any epidermal surface, including mucosal surfaces, but common warts are most often seen on the hands, feet, and knees. Verruca manifest as skin-colored hyperkeratotic papules. They may be pruritic, and scratching can produce a linear array of lesions via autoinoculation. The lesions are more prevalent in children and in immunocompromised patients; widespread, persistent lesions may be a clue to underlying inherited or acquired immunodeficiency.
For unknown reasons, the incidence of common warts is approximately twice as high in whites as in individuals of African descent, and 10 times more common in Hispanics than in individuals of African descent. In persons of African descent, the majority of warts are solitary, whereas in Hispanics, the common presentation is multiple warts.
Immunocompromised patients often have larger confluent verruca that are more resistant to standard therapies. The presence of warts per se is not a reason for expensive immunologic testing, however.
What to Look For: Look for 2- to 6-mm verrucous hyperkeratotic papules most commonly located on the dorsal surface of the hands, fingers, subungual skin, and feet. Close inspection will usually reveal tiny black dots, which represent thrombosed capillaries. Confluent verrucous plaques may form in sites of long-standing lesions. In immunocompromised patients, lesions may present as confluent verrucous plaques of up to 8 cm in diameter.
Acknowledgment: Image courtesy of Logical Images, Inc. (www.VisualDx.com/JUCM)