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Therapeutics in Dermatology
A reference textbook in dermatology

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Warts

12 July 2012, by PENSO-ASSATHIANY D.

Warts are caused by human papilloma viruses (HPV). They can occur anywhere on the skin or mucous membranes but are found mainly on the hands and feet. This chapter will not discuss mucosal locations, in particular genital warts (condylomas).

Warts can occur in isolation or in clusters. They are more or less painful, depending on the thickness of the stratum corneum where they occur.

Warts are transmitted through small breaks in the skin. They can also be transmitted at swimming pools and gyms and between family members.

Risk factors that increase the frequency of developing warts include atopy and immunosuppression related either to a treatment or to a disease.

Except in specific rare cases, there is no risk of progression to a dangerous lesion.

Since HPV viruses cannot be cultivated, it is difficult to elucidate the mechanisms by which they cause warts. There is no serological test that can be used.

There is also no known treatment of HPV infection, which makes the efficacy of wart removal treatments somewhat random. A local immune reaction explains why most warts regress spontaneously, particularly in adults.

In light of this information (benign nature, no antiviral treatment directed against the virus, random efficacy of wart removal treatments, possibility of spontaneous regression), it is reasonable to refrain from prescribing a harmful or aggressive treatment.

The main treatments can be divided into two main categories: physical treatments with liquid nitrogen, and chemical treatments, known as keratolytics, based on salicylic acid preparations.

Liquid nitrogen destroys the wart by freezing, causing a second degree burn. In the best of cases, this produces a blister and the wart falls off. Unfortunately, this method is often painful and does not always work after a single treatment. Instead, repeated treatments are required every two weeks or so.

Salicylic acid preparations have the advantage of being less painful but the drawback of having to be applied on a daily basis. The wart should also be scraped with a disposable emery board. Non-disposable items like a pumice stone, rasp or metallic file should be avoided because they are contaminated by viral DNA. The salicylic acid concentration varies according to location of the wart and is higher for plantar warts than for warts on the fingers. Various products with different salicylic acid strengths exist (M.O.Cochon® ointment, Transvercid®, Duofilm®,Kerafilm®, etc.), the highest strength (50% salicylic acid) being M.O.Cochon®

Other treatments, particularly laser and intralesional injection, are restricted to special indications.

The VRAIE trial on the treatment of plantar warts is currently being conducted in France. The aim is to identify the best strategy in the treatment of warts which did not cure after 5 weeks of M.O.Cochon® ointment. 

In conclusion, there are still a lot of unknowns in the field of wart viruses and wart treatments. Treatments should not be aggressive, and the comparable efficacy of properly conducted cryotherapy and keratolytic treatments will tip the scales according to the location of the wart and the patient’s age and expectations.

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