Warts

Warts are extremely commonplace in children and adolescents. The overall prevalence in school-aged children is 20%. Their prevalence sharply declines with increasing age.
In children, warts tend to regress spontaneously but this may take several years and in the meantime can be a significant source of emotional distress and a chief reason children seek medical attention.

Warts are caused by the human papillomavirus (HPV). The virus infects epidermal keratinocytes, which stimulates cell proliferation.
Viral transmission occurs primarily through skin-to-skin contact such as handshaking or kissing. The recently shed virus can also be found on moist, warm environments, including doorknobs, hand railings, floors of locker rooms, and around swimming pools.
Consequently, the virus is virtually impossible to avoid. Often, several family members develop warts. Whether this reflects a genetic susceptibility or is simply a result of the ubiquitous nature of the contagion has not been determined.
Minor skin abrasions, skin trauma, active dermatitis, or maceration can facilitate viral transmission.
Autoinoculation from the wart to adjacent skin is often seen especially for flat warts or warts on the fingers.
It is well documented that HPV can exist in a subclinical or latent state. This latency explains the frequent recurrence of warts at the same site or at an adjacent site, even when the warts had been apparently “cured” many years earlier.

Warts vary widely in shape, size, and appearance and are named according to their clinical appearance and/or location. For example, filiform warts are threadlike; planar warts are flat; and plantar warts are located on the plantar surface of the feet.
A typical wart is a papillomatous, corrugated, hyperkeratotic growth that is confined to the epidermis. Despite a common misconception, warts have no “roots,” and there is no “mother wart.”
Warts may be skin colored to tan and measure 5 to 10 mm in diameter. They may also coalesce into large clusters called mosaic warts.
Warts may develop anywhere on the body, but they are most often found at sites subject to frequent trauma, such as the hands and feet.
Although HPV can be transmitted during delivery or by autoinoculation, genital warts are uncommon in children and their presence should alert consideration for sexual abuse.

Common Warts

Common warts, also called verrucae vulgaris, occur most often on the hands and fingers often around (periungual) and under (subungual) the nails (Figs. 6.1 and 6.2). They are also frequently seen on the knees and elbows, especially in children.
Common warts are typically verrucose (vegetative) and exophytic and characteristically result in a loss or interruption of dermatoglyphics (fingerprints and handprints).
“Black dots,” representing thrombosed dermal capillaries, are pathognomonic (Fig. 6.3).
Distribution is generally asymmetric.
Common warts are usually asymptomatic, but can occasionally be tender and often cause embarrassment.

Based on clinical appearance.
A biopsy to confirm diagnosis is rarely needed.

Differential Diagnosis

Common Warts and Flat Warts

Molluscum Contagiosum

Dome-shaped shiny papules, central umbilication (see below).

Plantar Warts

Calluses

Broad-based hyperkeratotic plaques commonly found on the soles.
Distinguished from plantar warts because they reveal an accentuation rather than interruption of skin markings.

Management of Warts

General Principles

The management of warts is often challenging, and there is no ideal, 100% effective treatment (see Table 6.1).
The method of treatment depends on the following:
- The age of the patient
- The patient's pain threshold
- The type and size of wart
- The location of the lesion
- Cosmetic or psychological considerations
Treatments listed below are given in a step-wise fashion, beginning with the least painful, least aggressive methods. Oftentimes, multiple treatments with different mechanisms of action are utilized at once which increases efficacy and hasten resolution.

Home Treatment

Benign Neglect

Because most warts self-resolve, providing no treatment at all (“benign neglect”) may be safe and cost effective especially if few lesions are present in cosmetically inconspicuous locations.

Duct Tape (“Ducto-Therapy”)

In some studies, duct tape occlusion for stubborn common warts was as effective as treatment with liquid nitrogen.

Instructions

Cut a roll of shiny, electrical (duct) tape into strips slightly larger than the size of the wart.
Completely wrap the affected area with two “layers” of the tape (Illus. 6.1), making it airtight, but not wrapped too tightly.
If possible, the tape is left on for 6 days (during bathing, working, school, and all activities), and then removed for half a day. In children, the tape will likely need to be changed daily.
This procedure is repeated—6 days on, 6 days off; tape is changed daily.
- After several weeks the wart will become smaller, soft, and macerated and hopefully disappears.

Topical Salicylic Acid Preparations

Salicylic acid is a keratolytic (peeling) agent that can be self-administered. It exfoliates the hyperkeratotic “dead skin” of warts and induces inflammation.
Salicylic acid is available in varying concentrations, in numerous over-the-counter (OTC) trade name preparations such as Compound W gel and solution, Duofilm gel, patch, and solution (see Table 6.1 for a detailed list).
For best results with any keratolytic agent, the affected area should be hydrated first by soaking it in warm water for 5 minutes (or bathing) before application of the agent.
Topical salicylic acid is often recommended for at home use in between in-office treatments.

Advantages

Practical for periungual warts
Nonscarring
Painless to apply
Relatively inexpensive
Do not require office visits

Disadvantages

Slow response
Often no response
Time consuming

Over-the-Counter Cryotherapy

Salicylic acid preparations and OTC cryotherapy are among the most commonly used OTC treatments patients have tried before seeking medical attention.
OTC cryotherapy products use the combination of dimethyl ether and propane (Compound W Freeze Off or Dr. Scholl's Freeze Away) to freeze warts to 57°F.
Not as effective as cryotherapy with liquid nitrogen.

Immunotherapy: Interferon Induction

Topical imiquimod, available as a 5% (Aldara) or a 3.75% cream (Zyclara), induces production of interferons and and other cytokines that results in upregulation of cutaneous cell-mediated immunity.
Imiquimod is approved for the treatment of genital warts (discussed in Chapter 28: Sexually Transmitted Diseases); however, numerous reports have shown successful off-label use on common and plantar warts, and it is widely used as an adjunctive treatment for them.
Imiquimod cream is applied directly on the wart under duct tape occlusion after hydrating the area. This is best done at bedtime and washed off after 6 to 10 hours. It can be applied to facial flat warts without occlusion (see later discussion).

Topical Retinoids

Topical retinoids have antiproliferative and anti-inflammatory actions and are best for flat warts or as an adjunctive treatment for common warts as a second- or third-line option.

Topical Chemotherapy

5-Fluorouracil (5-FU) is a chemotherapeutic agent that prevents cellular replication and is used as a second- or third-line option for recalcitrant warts.
5-FU is applied directly on the wart with or without tape occlusion, which may enhance efficacy.
It is available in a 0.5% cream (Carac), 1% cream (Fluoroplex), or a 5% cream (Efudex) and as a 2% or 5% solution (Efudex). 5-FU can also be compounded with salicylic acid at compound pharmacies.

Oral Therapy

Oral cimetidine (Tagamet) has been reported to induce clearance of multiple warts in children and is believed to work by inhibiting suppressor T-cell function and boosting viral specific immunity.
Some studies have shown up to 80% clearance rates after 2 months of treatment.
The recommended dose for immunomodulatory effects is 40 mg/kg/day divided into twice-daily doses.
It is most often used as an adjunctive treatment in children with multiple, widespread warts that have been recalcitrant to other treatments.

In-Office Treatments

Cryotherapy with Liquid Nitrogen (LN₂)

Liquid nitrogen (LN₂) may be applied with a cotton swab or with a cryotherapy device (Cryogun) (discussed in Chapter 35: Diagnostic and Therapeutic Techniques). The goals are a rapid freeze and a slow thaw, which will induce physical destruction of viral infected cells and/or blister formation at the dermal-epidermal junction.
The treatment should freeze (turning it white) the wart and the surrounding 2- to 3-mm zone of skin. The freeze should last around 5 to 10 seconds. Longer freeze times may be used for thicker lesions.
Repeated freeze-thaw cycles increase cell damage and efficacy. Three freeze-thaw cycles is ideal.
The procedure is repeated at 2- to 3-week intervals, based on patient tolerance or on previous treatment results, degree of pain, and posttreatment morbidity.

Advantages

Treatment is rapid and highly effective.
Many lesions can be treated during a single office visit.
It works well for hand warts.

Disadvantages

Necessitates the availability of an LN₂ unit and a holding tank.
Treatment is painful and may be unacceptable for some children.
May result in painful blisters.
On darkly pigmented skin, cryotherapy can result in hypopigmentation or hyperpigmentation, or even depigmentation, because LN₂ can destroy melanocytes.
Overaggressive treatment may cause scarring.
Often requires multiple office visits.

Electrocautery and Blunt Dissection or Curettage

Electrocautery will burn the wart via the application of direct electrical current that conducts heat through a hot probe.
The burned wart is then easily removed at its base with a no. 15 blade or a curette and the base is cauterized.
Best for warts on the knees, elbows, and dorsa of hands; also effective for filiform warts.

Advantages

Tolerable in most adults.
Warts are removed on the day of treatment.

Disadvantages

Local anesthesia is required. Treatment sometimes necessitates a digital block, which can be painful, especially on the fingers and the soles of the feet.
May result in scarring.

Laser Ablation

Carbon dioxide (CO₂) laser destruction of warts is reserved only for large or refractory lesions.
CO₂ laser is expensive and requires local anesthesia.
Pulsed dye laser (PDL), targeting the thrombosed capillaries, has also been utilized as an adjunctive treatment of recalcitrant warts.

Sensitizing Agents

The deliberate induction of allergic reactions by injecting or applying sensitizing agents such as Candida skin test antigen (Candin), diphencyprone (DPCP), and squaric acid dibutylester (SADBE), are sometimes used to treat recalcitrant warts.

Vesicants

Cantharidin (Cantharone), or the so-called “blister beetle juice,” is a vesicant (blister-producing agent) that was originally derived from the green blister beetle and is most often used for treatment of molluscum contagiosum. It can be used for recalcitrant warts.
Cantharadin is thinly applied directly on the wart and allowed to dry completely in an office setting. It should be washed off in 4 to 6 hours. In 1 to 2 days a blister or crust will form at the site of application removing the wart.
Cantharone Plus is the combination of cantharidin, salicylic acid, and podophyllin in a flexible collodion and is a very potent alternative to Cantharone alone that may cause severe blisters and pain and should be used with caution.

Caustic Agents

Dichloroacetic acid, trichloroacetic acid, podophyllin, formaldehyde, and glutaraldehyde have all been used, with varying results.

Intralesional Chemotherapeutic Agent

Intradermal injections of bleomycin, a chemotherapy agent that inhibits cell division, is another treatment for highly resistant warts. This agent is expensive and may cause severe pain and tissue necrosis.

Surgical Excision

Surgical excision of warts is an option
Used for highly recalcitrant warts or for highly motivated patients

Helpful Hints for Treatment of Specific Types of Warts

Common Warts

First line in school-aged children: LN₂.
In between in-office treatments, use salicylic acid 17% under duct tape occlusion or salicylic acid 40% Band-Aids daily.

Plantar Warts

Paring with a no. 15 blade parallel to the skin surface often immediately relieves pain on walking.
The patient should be instructed to apply salicylic acid preparations between visits as follows:
1. Warts should be “sanded” with an emery board, foot file such as Dr. Scholl's Callous Removers, or a pumice stone.
2. After sanding, an OTC 17% salicylic acid solution (e.g., Salactic film) or a 40% salicylic acid plaster (Mediplast), cut to the size of the wart, is applied.
3. This product is left overnight. The plaster may be left on for 5 to 6 days.
LN₂, blunt dissection, electrodesiccation, and curettage are reserved for more recalcitrant warts or when patients insist on aggressive therapy.
Imiquimod cream under occlusion may also be used (see earlier discussion).

Flat Warts

First-line in-office treatments: cautious application of LN₂ therapy (e.g., with a cotton-tipped applicator) or low-intensity electrocautery.
Imiquimod cream (Aldara) or tretinoin cream (Retin-A), applied daily to lesions, are common first-line agents for flat warts in children; these can also be applied to lesions daily in between the above in-office destructive measures.

Filiform Warts

A virtually painless method is to dip a mosquito hemostat or a fine-tipped forceps into LN₂ for 10 seconds and then gently grasp the wart for about 4 to 5 seconds. The frozen wart is generally shed in 7 to 10 days (Fig. 6.8A,B). This method may require multiple office visits (see also Chapter 35: Diagnostic and Therapeutic Techniques).

Helpful Hints

In between in-office treatments, use salicylic acid solution or plaster as an adjuvant treatment to help achieve clearance sooner. Occlude the salicylic acid with duct tape.
Occlusion of topical home treatments such as salicylic acid or imiquimod may aid penetration and contribute to treatment efficacy.
Warts are highly contagious and are more likely to occur on diseased skin or skin with an impaired barrier. The best way to prevent development of a new wart or spreading of existing warts in patients with atopic dermatitis is to properly treat areas of active dermatitis and maintain a healthy skin barrier with the use of barrier repairing emollients.
How to avoid getting warts? Never shake hands. Never kiss anyone. Never walk barefoot. Never share towels. Live in a bubble… and there's still a good chance you'll get one.

Points to Remember

Consider psychosocial factors. For example, a 2-year-old child with a filiform wart located emanating from the nostrils, or those with multiple hand warts, should warrant less aggressive treatment than a 6-year-old child with similar lesions who may be subject to teasing by other children in school.
Freezing and other destructive treatment modalities do not kill the virus but merely destroy the cells that harbor HPV. In other words, when you treat a wart, only the “host” cells are destroyed, not the virus itself.
Because HPV persists after therapy, some degree of infectivity and the potential for recurrence may remain, even in the absence of clinical lesions.
Conservative, nonscarring treatments are preferred. A clinical “cure” is achieved when the skin lines are restored to a normal pattern and there is no recurrence.

Plantar Warts

Plantar warts (verrucae plantaris) occur on and surrounding the plantar surfaces of the feet, most often on the metatarsal area, heels, insteps (Fig. 6.4), and toes in an asymmetric distribution.
As opposed to common warts, plantar warts are usually endophytic and exhibit inward growth.
Plantar warts may be solitary or multiple, or they may appear in clusters called mosaic warts (Fig. 6.5).
As with common warts, there is loss of normal skin markings (dermatoglyphics) in the location of the wart, and pathognomonic “black dots” representing thrombosed dermal capillaries, which bleed easily after paring with a no. 15 blade (see Fig. 17.8).
May be tender and impair ambulation, particularly when present on a weight-bearing surface, such as the sole, heal, or metatarsal areas of the foot.

Flat Warts

Verrucae planae, or flat warts, are commonly found on the face, dorsa of hands, and legs.
Lesions are small, flat-topped minimally elevated papules that are skin colored or tan (see Fig. 17.10-17.12) to brown in color, and range in size from 1 to 5 mm (Fig. 6.6). Side lighting may be necessary to see them.
They may appear in a linear configuration due to autoinoculation (see Fig. 17.9).

Filiform Warts

Lesions present as tan, slender, delicate, finger-like growths that emanate from the skin and most commonly seen on the face—usually around the ala nasi (Fig. 6.7), mouth, eyelids, and on the neck.

Outline
Plantar Warts
Flat Warts
Filiform Warts

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Basics ⬇

Pathogenesis ⬆ ⬇

Clinical Manifestations ⬆ ⬇

Clinical Variant ⬆ ⬇

Diagnosis ⬆ ⬇

Other Information ⬆