2.1.4 Warts

Although almost certainly an under-estimate, common warts are reported to affect 7-10% of the population, most commonly in the first three decades of life.

Warts are a manifestation of infection of skin cells (keratinocytes) caused by human papilloma viruses (HPV). These are karyotropic DNA viruses with more than 100 types. Transmission is from human to human, or animal to human. The incubation period lasts from weeks to months. Predisposing factors to infection include impaired skin barrier (e.g. atopic eczema), immunosuppression (e.g. HIV, those undergoing chemotherapy etc), hyperhidrosis, impaired peripheral circulation and occupation (e.g. jobs involving hands soaked for hours in water, butchers etc).

The lesions form after a superficial keratinocyte infection by one of the many types of human papilloma virus.

Any part of the body may be infected, depending on exposure. The hands and feet are most typically affected.

Classification is according to HPV subtype:

• verruca vulgaris: common wart (HPV 1, 2);

• v. plantaris: plantar, mosaic warts (HPV 2, 4);

• v. plana: (HPV 1, 3).

However, it is not possible to be completely reliable on differentiating different wart types on clinical grounds alone.

Most common warts resolve spontaneously, however this may take months or even years.

Warts have a tendency to persist and become disseminated in immunocompromised individuals. If there are warts around the fingernail, sometimes a permanent nail dystrophy may occur. Some HPV subtypes may lead to neoplasia including squamous cell carcinoma.

Corns, macrocomedones, lichen planus, Darier’s disease, condylomata lata (Syphilis II), squamous cell carcinoma. Plantar localization includes also amelanotic malignant melanoma.

Spontaneous resolution is seen in 95% of patients within 2 years. Aggressive therapy should therefore be avoided, especially in small children. Beware scarring from over- treatment. Surgery is only very rarely indicated. Cryosurgery, electrocautery, keratolytics (e.g. salicylic acid), topical retinoids (for facial involvement), 5-fluorouracil (5-FU), diphenylcyclopropenone immunotherapy (DCP) and imiquimod should be considered as treatments where appropriate.