Common Skin Infections

WARTS

These are predominantly caused by -

•  Poxviruses
•  Papilloma viruses

Warts are caused by Human Papilloma viruses (HPV) which infect and replicate in squamous epithelium. They enter the skin through small abrasions. The incubation period is probably a matter of months.

Common warts: firm papules with a rough horny surface. They are commonest over the knuckles and nail folds, and can also occur on the knees and on the shaft of the penis. They are caused by HPV 1, 2 and 4.

Common warts on fingers

• Plantar warts (verrucae) generally occur at pressure points. They start as a small papule and as they enlarge small thrombosed capillaries may be seen in the tips of the elongated papillae.
• Plane warts: smooth, flat or slightly elevated, occurring on the face or the back of the hands. They may form lesions at the site of abrasions (Koebner’s phenomenon). They are caused by HPV 3 and 5.

Plane warts

• Filiform warts are common in the beard area, on the lips and in the nasal vestibule.

Filiform wart

• Mosaic warts consist of clusters of small warts.
• Benign condylomata (genital warts) are caused by HPV-6 and 11. Classical genital warts are multiple, pointed, and fissured.  In women they occur most commonly at the posterior introitus and adjacent labia; also the vulva, perineum, vaginal wall and cervix (a smear should be taken). Warts enlarge during pregnancy and may occasionally obstruct the vagina. In men warts may occur on the frenum, coronal sulcus or glans. Intrameatal warts may spread into the urethra. Perianal warts may spread into the anal canal. They can occur in both homosexual and heterosexual men. HPV 16 +18 appear to risk factors for genital malignancy, and are found in approximately a third of malignancies. However, note that direct transformation from wart to malignancy appears to be very rare. HPV can also be found in cells from a normal cervix. In the UK a recently introduced vaccination programme for 13+ year old girls is aiming to reduce cervical cancer rates by prevention of HPV infection.

Treatment

BAD Wart Treatment Guidelines

Most will resolve spontaneously. Genital warts regress less frequently than skin warts.

There are a wide variety of treatments for warts as below. The best evidence base exist for either salicylic acid or cryotherapy. I often try and persuade patients to do nothing if possible!!

• Salicylic acid 20-40% is effective when applied as a paint or plaster after soaking the skin for 5 mins with warm water. The surrounding skin should be protected with a ring of vaseline 
• Cryotherapy may be used without anaesthesia but is often not practical for large warts.
• Formalin 10% can be used as a soak for multiple warts on the soles of the feet.
• Fluouracil 5% cream or solution (Efudix®) may be used either alone or alternating with topical retinoids in the treatment of plane warts.
• Podophyllin 10-20% in liquid paraffin may be painted onto anogenital warts and the area then powdered. The coating may be washed off 3-4 hours later. The treatment is repeated 1-3 weekly. It can be irritant and should not be used in pregnancy due to the risk of systemic absorption and damage to the foetus. It should also not be used on the cervix, because of the risk of neoplastic change. If a local reaction occurs the treatment should be stopped and 1% hydrocortisone applied topically twice daily until the inflammation has resolved. The treatment can then be tried again with caution.
• Imiquimod (5%), an immunomodulator, has recently been introduced for genital warts, and trials are ongoing in cutaneous warts. 
• Electrocautery may be used for some types of warts but must be done using local anaesthesia. 
• Surgical excision may occasionally be used to remove or debulk extensive warts, especially perianal warts.
• Laser evaporation using a carbon dioxide laser can be used for both mucosal and cutaneous lesions.
• Loop electrosurgical excision procedure (LEEP) uses a heated loop to remove cervical lesions. The lesions is removed intact and can be sent for pathological examination
• There is evidence against using Cimetidine.