Viral infections – Warts and other viral infections
Unlike bacteria and yeasts, viruses are not thought to exist on the skin surface as commensals. However, studies in patients with viral warts have shown viral DNA in epidermal cells of seemingly normal skin next to warty areas.
Viral warts
Aetiopathogenesis and pathology
Over 96 subtypes of DNA HPV have been identified. The virus infects by direct inoculation and is caught by touch, sexual contact or at the swimming baths. Certain HPV subtypes are associated with specific clinical lesions, e.g. types 2, 27 and 57 with common hand warts, types 1, 2, 4, 27 and 57 with plantar warts, types 3 and 10 with plane warts, types 6 and 11 with genital warts. Genital HPV subtypes cause cytological dysplasia of the cervix, which may be precancerous. Immunosuppressed individuals, such as those with organ transplants, are particularly susceptible to viral warts (p. 57). The epidermis is thickened and hyperkeratotic. Keratinocytes in the granular layer are vacuolated due to being infected with the wart virus.
Clinical presentation
Certain clinical patterns are well recognized:
Common warts. These present as dome-shaped papules or nodules with a papilliferous surface. They are usually multiple, and are commonest on the hands (Fig. 1) or feet in children but also affect the face and genitalia. Their surface interrupts skin lines. Some facial warts are ‘filiform’ with fine digit-like projections.
Plane warts. These are smooth flat-topped papules, often slightly brown in colour, and commonest on the face (Fig. 2) and dorsal aspects of the hands. They are usually multiple and resist treatment, but eventually resolve spontaneously, often after becoming inflamed. They can show the Koebner phenomenon.
Genital warts. In males, these affect the penis and, in homosexuals, the perianal area. In females, the vulva, vagina and perianal area maybe involved (Fig. 3). The warts may be small or may coalesce into large cauliflower-like ‘condylomata acuminata’. Proctoscopy (if perianal warts are present) and colposcopy (for female genital warts) are needed to identify and treat any rectal or cervical warts because of the risk of neoplastic change. Sexual partners need to be examined.
