Cutaneous warts

The diagnosis of warts is usually straightforward but treatment can be difficult, says Dr Raj Thakkar.

Verruca vulgaris are commonly seen on the knees (as above) (Photograph: SPL)
Verruca vulgaris are commonly seen on the knees (as above) (Photograph: SPL)

Warts, caused by many strains of human papilloma virus (HPV), are commonplace in general practice, with a prevalence of 10-30 per cent among primary school children and a very high life-time risk.1

The diagnosis is usually straightforward, but the treatment is often difficult, due to patients' expectations of a quick resolution, the location of the wart, the persistence of the wart itself as well as the absence of a reliable evidence base.

Warts are more prevalent, persistent and aggressive in immunocompromised patients. This article focuses on cutaneous warts in immunocompe-tent patients.

1. Infection
HPV is highly contagious and its incubation period may be weeks or even months. In addition to HPV being transmitted by direct skin-to-skin contact, it may be passed indirectly, for example by sharing towels or shoes, or at swimming pools and other wet facilities.

Wet, soft, cut and exposed skin is more prone to infection by HPV. Cutting and scratching warts may disperse the virus, which is why shaving can pose a high risk of infection.

Scratching a wart may transfer the virus to the fingers causing further self-inoculation or indeed trans- mission to others.

2. Presentation
Both the appearance and size of warts can vary dramatically, and partly depend on the strain of HPV involved. Some are small while others may grow to more than 10mm in diameter. For most patients, the main concern is cosmetic issues, particularly if they grow on the face.

Filiform warts, otherwise known as verruca filiformis, are often seen on the face and nostrils. They have long, hair-like projections, which promotes a significant cosmetic burden.

Common warts, also referred to as verruca vulgaris, tend to be round and cauliflower-like in appearance. This type of wart is most commonly seen on the hands and knees.

Verruca plantaris appears rough and white, sometimes with a black blood vessel at its core. Verruca plantaris may be painful to walk on.

Plane warts tend to be no bigger than four millimetres in diameter and often affect the face and hands of young children. Leg shaving may also pre-dispose women to plane warts. This type of wart tends to appear in clusters, which may contain more than a hundred lesions.

Mosaic warts also grow in clusters and tend to occur on the palms of the hands and soles of the feet.

Warts may grow either around or even underneath finger or toenails. These peri-ungual warts may be painful and distort the affected nail.

Key points
  • Warts are more prevalent, persistent and aggressive in immunocompromised patients.
  • Both the appearance and size of warts can vary dramatically.
  • Between 65 and 80% of lesions will be cleared by immunocompetent people within two years without treatment.

3. Management
The treatment for warts remains controversial. Between 65 and 80% of lesions will be cleared by immunocompetent people within two years without treatment. The like-lihood of spontaneous resolution is higher in children than in adults. Some data suggest a watch-and-wait policy in children is no less effective than active treatment, at least for verruca vulgaris and plantaris.1 In this case, treatments should only be considered if the warts cause pain or affect functioning.

Cryotherapy may come in a number of forms, including liquid nitrogen as well as OTC alternatives (dimethyl ether/propane).

It has been shown that cryotherapy with liquid nitrogen is more effective than salicylic acid or a watch-and-wait approach in the treatment of verruca vulgaris but there is no significant difference in these treatments for the management of verruca plantaris.2

Certainly, other studies have shown no meaningful difference between cryotherapy and self-treatment with salicylic acid 50% in the management of verruca plantaris in patients over the age of 12 years.3 Cryotherapy is the first-line therapy for filiform warts.

While the evidence promoting the efficacy of combination cryotherapy and topical salicylic acid is unconvincing, there is evidence to support the use of topical salicylic acid over placebo, and in addition, the side-effect profile is favourable compared with cryotherapy.

Some data offer an NNT of four with topical salicylic acid 50% compared to placebo, and furthermore, an NNT of two with intense treatment of verruca plantaris with 60% salicylic acid combined with trichloroacetic acid. Formaldehyde may be particularly effective in the treatment of mosaic warts.4

The British Association of Dermatologists suggests there is evidence that duct tape is effective in the management of warts.4

A number of other treatments are available for cutaneous warts such as glutaraldehyde, podophyllin, 5-fluorouracil, imiquimod, candida antigen injection, curettage, cautery, laser and surgery.

The evidence for cutaneous wart treatment is not entirely clear. Nevertheless, there are some trends that emerge from the literature: it is very reasonable, especially in children, to adopt a watch-and-wait policy as spontaneous clearance is common and treatment not necessarily practical.

Lesions on the face, or those causing pain deserve special consideration. Daily salicylic acid preparations are generally as efficacious as cryotherapy but have fewer adverse effects.

  • Dr Thakkar is a GP in Wooburn Green, Buckinghamshire

Reflect on this article and add notes to your CPD Organiser on MIMS Learning

1. Bouwes Bavinck JN, Eekhof JAH, Bruggink SC et al. Treatments for common and plantar warts. BMJ 2011; 342: d3119.

2. Bruggink SC, Gussekloo J, Berger MY et al. Cryotherapy with liquid nitrogen versus topical salicylic acid application for cutaneous warts in primary care: randomized controlled trial. CMAJ 2010; 182: 1624-30.

3. Cockayne S, Hewitt C, Hicks K et al. Cryotherapy versus salicylic acid for the treatment of plantar warts (verrucae): a randomised controlled trial. BMJ 2011; 342: d3271.

4. The British Association of Dermatologists. Patient information leaflet on plantar warts.

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