Dermatology Essentials
2. Warts
Betty Nguyen
If you rotate through any dermatology clinic, you are almost certain to see at least a few patients with warts (also known as verrucae). Although warts can be bothersome for some patients, the good news is that they usually resolve on their own with time.
But when do you treat them? And with what? Are there different types of warts? Does every patient get cryotherapy? And what about refractory warts? This guide will provide a high level overview.
Etiology & Risk Factors
Warts are caused by infection with a type of human papillomavirus (HPV), which is thought to enter the body through damaged areas of the skin. Although warts occur more often in children and young adults, they can affect people of all ages. There are several risk factors for warts, including:
1. Handling meat, poultry, and fish
2. Using public showers and pools
3. Atopic dermatitis (eczema)
4. Weakened immune system
Types of Warts
Warts are classically divided into three types:
1. Common warts (verruca vulgaris): usually located on the fingers or back of the hand, but can be anywhere on the body (often where there can be trauma)
2. Plantar/palmar warts (verruca plantaris/palmaris): located on the palms of the hand or soles of the foot
3. Flat warts (verruca plana): usually on the face, back of the hands and arms, or legs
The diagnosis of cutaneous warts is based on clinical appearance, so take a moment to remind yourself what each type looks like:
Figure 1: Types of Warts
A) Common wart (verruca vulgaris)
B) Plantar/palmar wart (verruca plantaris/palmaris)
C) Flat warts (verruca plana)
Treatment
Because warts usually resolve on their own with time, treating all patients with warts is not necessary. If, however, a patient desires treatment (due to pain, discomfort, or functional/cosmetic concerns), several options are available.
The two most common first-line treatments for warts are:
1. Topical salicylic acid
2. Cryotherapy with liquid nitrogen
Salicylic acid works by exfoliating the epidermis until the wart is gone. The acid may also stimulate a local immune response that promotes formation of healthy skin cells in the area. In most cases, daily treatment with salicylic acid removes the wart within 3 months.
Cryotherapy works by using extreme cold (liquid nitrogen) to destroy skin tissue. One disadvantage of cryotherapy is that it can be painful, so it is generally avoided in younger children.
Refractory Warts
Treating warts that are not self-resolving and are refractory to first-line treatments is less straightforward. Some treatment options include:
1. Topical immunotherapy with contact allergens (e.g. DPCP or SADBE)
2. Intralesional bleomycin
3. Intralesional or topical fluorouracil
Topical immunotherapy with contact allergens, such as diphenylcyclopropenone (DPCP) and squaric acid dibutylester (SADBE), involve first sensitizing the patient to the contact allergen by applying the sensitizer to a small unaffected area. Application of the contact allergen to the wart typically begins two weeks after sensitization, with the goal of maintaining a mild contact dermatitis in the affected area, which aids in wart removal.
Bleomycin is a chemotherapeutic agent with cytotoxic and antiviral effects. The disadvantage of intralesional bleomycin is that it can cause significant pain that lasts 1-2 days, followed by black eschar formation. Due to systemic absorption, intralesional bleomycin is not recommended in children, pregnant women, and immunocompromised patients.
Fluorouracil is an antimetabolite that suppresses wart growth by inhibiting DNA and RNA synthesis. Intralesional fluorouracil can cause pain at the time of injection, but this pain is less and shorter lasting than pain from intralesional bleomycin. Topical fluorouracil is usually applied daily under occlusion.
In addition to these treatments, you may also hear of other options, such as intralesional immunotherapy with skin test antigens (e.g. Candida), cantharidin, imiquimod, trichloroacetic acid, duct tape, pulsed dye laser, and oral cimetidine. However, current evidence for these treatments are limited or conflicting, and these are generally used in conjunction with first-line therapies.
Conclusions
1. Warts, also known as verrucae, are a common dermatologic complaint caused by infection with HPV.
2. Warts are classically divided into three types: common warts, palmar/plantar warts, and flat warts.
3. First-line therapies for warts are topical salicylic acid and cryotherapy with liquid nitrogen.
4. Treatments for recalcitrant warts include topical immunotherapy with contact allergens, intralesional bleomycin, and intralesional or topical fluorouracil.