Epidemiology^[1]

Warts are very common and affect 7-12% of the population. 10-20% prevalence has been reported for school-age children. Increased prevalence is seen in immunosuppressed patients and meat handlers. White people are twice as likely as black people or those of Asian descent to develop warts. There is no gender predilection.

Appearance^[1]

Common warts appear as papules and nodules with a keratotic and papillomatous surface. They occur anywhere but are most common on the hands in young people and children.

Other types include: Filiform warts - these are small finger-like warts consisting of hyperkeratotic projections.

Palmar warts - thick keratotic warts that may be painful on pressure.

Mosaic warts - these are groups of plantar, or occasionally palmar, warts.

Plane warts - these are slightly elevated, flat-topped warts which may occur singly or in a group of many lesions.

Diagnosis^[1]

This is usually obvious but, if necessary, paring down will produce tiny pin point bleeding of the capillaries in the roots of the wart.

Differential diagnosis^[1]

• Actinic keratosis
• Arsenical keratosis
• Cutaneous horn
• Genital warts
• Lichen nitidus
• Lichen planus
• Molluscum contagiosum
• Prurigo nodularis
• Seborrhoeic keratosis
• Squamous cell carcinoma

Aetiology ^[2][3]

They are caused by the human papillomavirus (HPV). Trauma and wetness are contributory in contracting warts.

Management^[1][2]

• Warts may require no treatment if the patient is happy to tolerate them but they may wish to have them treated for the sake of appearance or because they are causing discomfort.
• Keratolytic agents can be used if they are numerous or large. Topical salicylic acid has the largest evidence base.^[4]
• Patients can treat small warts at home, using salicylic acid available from a pharmacy without prescription. Keratolytics should not be used on the face.
• Multiple small warts are best treated with cryotherapy. Cryotherapy sprays containing dimethyl ether and propane are available for purchase without prescription and are becoming increasingly popular.
• One study found no statistical difference in terms of outcome between cryotherapy and application of 80% phenol in the treatment of warts of the hands.^[5] Another found equivalent effectiveness between cryotherapy and salicylic acid.
• Topical treatments sometimes used include glutaraldehyde and formaldehyde..
• Single larger warts can easily by removed by curettage and cautery.
• Persistent warts may need removal by curettage and cautery.
• Treatment with the pulsed dye laser is effective in stubborn warts on fingers. This works by ablating the blood vessels within the wart. Multiple treatments are needed.
• Treatments currently being evaluated include antimitotic therapy such as bleomycin and retinoids, the topical chemotherapy agent 5-fluorouracil and immune stimulators such as dinitrochlorobenzene.
• Intralesional injections being studied include Candida, mumps, or Trichophyton skin test antigens, bleomycin and interferon-alfa.
• One study found that photodynamic therapy combined with topical 5-aminolevulinic acid was beneficial.
• Systemic retinoids and intravenous cidofovir have been useful for the treatment of extensive, disfiguring and recalcitrant warts.
• Alternative treatments tried with varying degrees of success include hypnosis, occlusion therapy with duct tape, garlic, hyperthermia, propolis and tea tree oil.

When to refer^[2]

Justifiable reasons to refer to secondary care include:

• Persistent warts unresponsive to primary care treatment.
• Multiple warts in immunocompromised patients.
• Facial warts.
• Extensive coverage (eg mosaic warts).

Prognosis

Approximately 65% of warts will disappear within two years,^[1] although in few individuals they may persist for a long time.^[6]

Prevention

The risk of auto-inoculation can be reduced by avoiding biting the area (eg nail biting), trauma and maceration of the involved skin. Vaccines are currently being investigated.