Viral warts

Warts (verrucae) are common cutaneous tumours due to infection via direct inoculation of epidermal cells with human papilloma virus (HPV) and most people will experience them at some time in their life (Figure 12.6). They are spread by touch, sexual contact or indirectly via fomites or inanimate objects or substances capable of carrying infectious organisms. They are common in children and the immunosuppressed are particularly susceptible. Approximately 50% of renal transplant patients develop warts within 5 years of transplantation. The epidermis becomes thickened and hyperkeratotic due to vacuolation of keratinocytes infected by the wart virus whereby the keratinocytes become filled with fluid-filled vesicles bounded by a membrane within the cytoplasm. Up to half of common warts disappear spontaneously in children within 6 months. Benign warts almost never undergo malignant transformation in immunocompetent individuals. Sterling et al. (2001) advise that periungual warts in combination with genital HPV disease warrant careful attention. In immunosuppressed patients, dysplastic change is quite common and there is often a poor correlation between clinical and histological appearance.