Pathogenesis

Verrucae (warts) are cutaneous and/or mucocutaneous infections of keratinocytes caused by human papillomavirus (HPV). There are more than 100 subtypes of HPV, with some subtypes affecting characteristic skin locations. In most cases, the infection follows direct inoculation of the skin by HPV, presumably through minor (imperceptible) skin breaks. In the United States, the lifetime risk of developing a clinically-relevant HPV infection has been estimated to be about 80%.

Clinical Features

• •
  

  Verrucae can occur in any age group but are most common in young children.

  
  
• •
  

  Verrucae can affect any cutaneous site and, occasionally, mucosal surfaces.

  
  
• •
  

  Lesions present as skin-colored verrucous papules or plaques ( Figs. 28.1 and 28.2 ), often with overlying scale, which can disrupt normal skin lines (dermatoglyphs). There may be black dots that represent thrombosed capillaries, and this phenomenon can be called “seed warts” by patients.

  
  

  
  

  
  

  

  
  

  
  

  Multiple periocular verrucae in a child, always a therapeutic challenge.

  
  

  (From the William Weston Collection, Aurora, CO.)

  
  

  
  

  
  

  

  
  

  
  

  Patient with multiple periungual warts. The periungual and subungual regions are particularly challenging to treat.

  
  

  (From the William Weston Collection, Aurora, CO.)

  
  
  
  
• •
  

  Verrucae often occur on the hands (verrucae palmaris) or feet (verrucae plantaris; Fig. 28.3 ).

  
  

  
  

  
  

  

  
  

  
  

  Patient with plantar wart.

  
  

  (From the Fitzsimons Army Medical Center Collection, Aurora, CO.)

  
  
  
  
• •
  

  Myrmecia (Greek for “ant”) represent endophytic verrucae caused by HPV1 that occur upon the feet (common) or hands (less common). Myrmecia may be painful.

  
  
• •
  

  Destructive modalities may spread a wart in peripheral fashion, causing a so-called “fairy ring” of lesions ( Fig. 28.4 ). Still, these treatment modalities are widely used, and the risk is often tolerated.

  
  

  
  

  
  

  

  
  

  
  

  Patient with the frustrating fairy ring wart that occurred after cryotherapy. The wart has recurred in the margins of the blister, plus the patient now also has a scar from the therapy.

  
  

Diagnosis

• •
  

  The diagnosis is often based chiefly upon the clinical appearance of the lesion.

  
  
• •
  

  It can be difficult to distinguish plantar warts from corns and callosities because both cause overlying scale. Lesions may be removed from this overlying keratin with a scalpel blade to examine the base. Plantar warts demonstrate a loss of normal skin lines (dermatoglyphs), whereas corns and callosities retain such markings.

  
  
• •
  

  Problematic cases can be sampled by a deep shave and submitted for histologic examination.

Treatment

• •
  

  Over-the-counter treatments are usually based on topical salicylic acid, with or without other additives, such as lactic acid. The response rate is from 40% to 84% (average, 61%). Other topical therapies used include cantharidin (so-called “blister beetle juice”), imiquimod, tretinoin, and 5-fluorouracil.

  
  
• •
  

  Liquid nitrogen (LN ₂ ) cryotherapy is a destructive therapy often used by health care providers. In published studies, the cure rate of LN ₂ is between 26% and 96%. Optimal results are achieved with treatment every 2 to 3 weeks. Plantar warts respond better if excess keratin is pared before LN2 treatment and if two freeze-thaw cycles are employed.

  
  
• •
  

  Occlusion with duct tape was widely reported in the lay press a number of years ago. Medical evidence suggests the efficacy of duct tape is highly variable.

  
  
• •
  

  Immunotherapy includes topical sensitization with diphencyprone or squaric acid dibutylester or the intralesional injection of Candida antigen.

  
  
• •
  

  Systemic therapies for recalcitrant warts include oral cimetidine and oral retinoids. The efficacy of these modalities, particularly cimetidine, is dubious.

  
  
• •
  

  Laser therapy is usually performed with a carbon dioxide laser or flashlamp pulsed dye laser. The first is an ablative laser, whereas the latter targets the increased blood supply that is present in verruca.

  
  
• •
  

  Intralesional therapies include bleomycin, interferon, and formic acid, but these modalities are usually reserved for the most recalcitrant verruca.

Clinical Course

About 40% to 70% of verrucae resolve spontaneously, usually in about 2 years.

Pathogenesis

Verrucae plana, also known as flat warts, are usually caused by HPV3. Because of differences in the clinical presentation and management, it is useful to discuss separately verrucae plana.

Clinical Features

• •
  

  Verrucae plana are more common in children and young adults but can affect any age group.

  
  
• •
  

  Verrucae plana usually occur on the face and dorsal hands but can also affect the trunk and lower extremities.

  
  
• •
  

  Lesions are typically numerous and may number in the hundreds.

  
  
• •
  

  The primary lesion is a skin-colored to tan to light brown small papilloma that rarely exceeds 3 mm in diameter ( Figs. 28.5 and 28.6 ).

  
  

  
  

  
  

  

  
  

  
  

  Patient with numerous small tan papillomas in a perioral distribution of focal coalescence into a small plaque.

  
  

  (From the William Weston Collection, Aurora, CO.)

  
  

  
  

  
  

  

  
  

  
  

  Patient with numerous small tan, flat warts that are clinically difficult to distinguish from small seborrheic keratoses.

  
  
  
  
• •
  

  Lesions may become inflamed, with a red or violaceous color ( Fig. 28.7 ).

  
  

  
  

  
  

  

  
  

  
  

  Patient with verrucae plana with autoinoculation at a site of a superficial injury. These lesions are violaceous in color due to inflammation.

  
  
  
  
• •
  

  Lesions may appear in a linear configuration due to autoinoculation (see Fig. 28.7 ).

  
  
• •
  

  Variations include a so-called “intermediate wart,” which has features of both a flat and common wart.

  
  
• •
  

  Epidermodysplasia verruciformis (EV) is a genetic predisposition to extensive flat warts caused by HPV5, HPV8, HPV14, or HPV17. Lesions of EV may mimic other neoplasms or inflammatory conditions ( Fig. 28.8 ). Lesions of EV have some oncogenic potential, and squamous cell carcinoma can arise in some cases.

  
  

  
  

  
  

  

  
  

  
  

  Numerous inflamed red flat papillomas on the trunk in a patient with epidermodysplasia verruciformis.

  
  

Diagnosis

• •
  

  In most cases, the occurrence of multiple, small, uniform skin-colored to brownish papillomas is diagnostic. In some cases, it may be difficult to distinguish verrucae plana from other papillomatous conditions, such as seborrheic keratosis.

  
  
• •
  

  Problematic cases, including lesions in adults, truncal lesions, and inflamed lesions, should be biopsied to clarify the diagnosis. The findings are often specific (koilocytosis).

Treatment

• •
  

  Verrucae plana can be difficult to treat, and if the lesions are few in number and are not bothersome, therapy is not required. Treating numerous lesions may be challenging.

  
  
• •
  

  If treatment is desired, nonscarring modalities, such as topical tretinoin gel (0.025%–0.1% applied qd), is a reasonable option.

  
  
• •
  

  Topical imiquimod cream (applied three times/week for up to 16 weeks) is also a reasonable choice.

  
  
• •
  

  Recalcitrant cases may be treated with ablative lasers.

  
  
• •
  

  Destructive modalities (e.g., LN ₂ , electrodessication) may be utilized but can cause scarring, and for this reason, such modalities are often avoided on the face.

Clinical Course

Most verrucae plana will resolve without treatment, usually over 2 to 3 years. EV often persists longer and also has the potential to eventuate into squamous cell carcinoma, on occasion.