Description

Verrucae or plantar warts are hyperkeratotic lesions found particularly over the pressure areas of the feet (heel and ball). They are usually self-limiting but may be treated if symptomatic.

Natural history

• Half will disappear within 1 year
• Two-thirds disappear after 2 years
• Remaining one third more resistant and persistent

Pathophysiology

They are caused by the human papilloma virus (types 1 and 2 mainly but also 4). They affect epithelial cells causing small rough papules. Replication of the virus within the epithelial cells causes a proliferative reaction and formation of plaque or papule. Incubation is very variable, ranging from 1 month up to 2 years.

Transmission¹

• They are spread by person-to-person contact
• Use of communal showers is associated with higher rates of plantar warts²
• Infection is more likely if skin is macerated
• Scratching, nail-biting, finger-sucking and shaving all encourage auto-inoculation of viral warts
• They should not be used as a reason to stop children swimming, as learning to swim is important in the National Curriculum and helps prevent death from drowning^3,4
• They may be covered (with waterproof plasters or socks) when swimming but this can stigmatise children, and there is no evidence that these measures prevent spread⁵

Epidemiology

Data are limited, but:

• They are widespread and some report as many as 10% of the population affected at any time
• Most people get them at some time in their lives
• They appear to affect women marginally more than men
• They are more common with peak incidence in children and teenagers (affect about 4-5%)
• They are uncommon in infants
• They are more common particularly on the hands in eczema and with certain occupations (butchers, abattoir workers, engineers, office workers)

Presentation

• History
  • They may cause pain, particularly with walking
  • Occasionally leg or back pain may result from altered posture or gait disturbance
  • May be found in other family members
  • More common in:
    • Certain occupations
    • Atopic eczema
    • Impaired cellular immunity (usually numerous and resistant):
      • Long-term immunosuppressant usage
      • AIDS
      • Transplant patients
      • Lymphomas and leukaemias
• Examination
  • Firm, hyperkeratotic lesions
  • May have minor pinpoint petechiae centrally within the lesions
  • Usually found over pressure areas
  • Flat because of pressure
  • May fuse with surrounding warts (mosaic warts)
  • May occasionally be difficult to differentiate from other conditions (see Differential diagnosis below)

Diagnosis

Diagnosis is made by examination and observation of typical features:¹

• Common warts are common on knuckles, knees and fingers. They are firm and raised with a rough, cauliflower-like surface.
• Plane warts are round, flat-topped, and often yellow in colour. They are common on the dorsal surface of hands.
• Filiform warts are long and slender. They are common on the face and neck.
• Plantar warts or verrucae grow on the soles of the feet. They may be painful. They often have black dots within them.
• Mosaic warts occur when palmar or plantar warts join up to form large plaques on the hands and feet.

Differential diagnosis

• Corns: these are inflamed and painful. Paring corns reveals pearly sections of keratin.
• Calluses: these are thick and painless patches of hard skin.
• Black heel: patches of hard skin with ruptured capillaries.
• Verrucous squamous cell carcinoma: this should be considered if longstanding. They invade the dermis but are slow-growing and rarely metastasise.

Investigations

None usually required or appropriate. Distinguishing them from corns may require paring of the keratin as above. Blood tests to check for causes of immunodeficiency may be required in unusually widespread or resistant cases.

Associated diseases

Usually none. However, consider drugs and diseases affecting particularly cellular immunity.

Management^1,6

• Education about the natural history
• Usually no treatment if not painful
• More likely to want or need treatment if:
  • Painful
  • Immunosuppressed
  • Resistant cases (present for 2 years or more)
  • Patient choice in full knowledge of natural history
• Choices of treatment include:
  • Salicylic acid preparations:
    • Several brands available over-the-counter
    • Plasters
    • Collodion
    • Gel
    • Paint
    • Combined with podophyllum resin
  • Formaldehyde and glutaraldehyde preparations - unpleasant and used less often
  • Cryotherapy - usually 2 to 4 treatments (using a 1-minute freeze/thaw cycle after paring away excess keratin) 4 weeks apart
  • Rarely used methods include surgical excision, curettage, 5-fluorouracil, interferons, photodynamic therapy and bleomycin injection

A recent study suggests that salicylic acid preparations (over-the-counter use) were the most cost-effective treatments and that nurse-administered cryotherapy was more cost-effective than GP-administered cryotherapy.⁷ Generally speaking there is a lack of evidence for efficacy and cost-effectiveness of treatments.⁸ Banana skins, witchcraft and hypnosis also have their advocates.^9,10

Complications

• Secondary to treatment:
  • Pain
  • Infection
  • Scars and keloid formation
• Psychological
• Malignant change: extremely rare, especially with normal immunity. Rarely occurs but be aware of the possibility in patients who are immunocompromised (for example transplant patients)

Prognosis¹

It should be borne in mind that:

• Treatment failure is common
• Verrucae may be impossible to get rid of in the immunocompromised patient
• Two thirds will disappear after 2 years without treatment
• 90% of warts present at age 11 years, will be gone by age 16 years

Prevention

There is no evidence that using verruca socks prevents spread and the possible stigmatising effect of wearing such socks suggests use should be discouraged. Suggestions for reducing spread include:¹

• Cover the with a waterproof plaster when swimming.
• Wear flip-flops in communal areas and showers.
• Avoid sharing shoes, socks or towels.
• Limit auto-inoculation by avoiding trauma (scratching and biting), keeping feet dry and changing socks daily.