How To Treat Recalcitrant Plantar Warts

Christina A. Weber, DPM, FACFAS, and Kristine M. Hoffman, DPM

Treatment for recalcitrant plantar warts can be time-consuming and the options for treatment have differing levels of success. Accordingly, the authors share pearls and case studies from their clinical experience as well as insights from the literature on modalities ranging from topical agents and surgical excision to oral therapies and pulsed dye lasers.

The treatment of warts can be very challenging. Wart treatment is indicated for numerous reasons including irritation, pain, cosmetic embarrassment and risk of transmission. Many warts fail to respond to conventional treatment and after several months are considered recalcitrant. Recalcitrant warts require a more aggressive and focused treatment approach.
Accordingly, let us take a closer look at current and emerging modalities for recalcitrant warts.

   Warts (verrucae) involve the epithelium of the skin and are caused by infection with the human papillomavirus (HPV). Warts are the most common viral infection of the skin, affecting 7 to 10 percent of the general population.1 Plantar warts are benign proliferations of epithelial cells on the soles of the feet. Plantar warts are most often caused by infection by HPV types 1, 2, 4, 60 or 63.1 The human papillomavirus thrives in warm, moist environments, such as public swimming pools and locker rooms, and transmits by direct contact, possibly through small cuts or abrasions in the stratum corneum layer of the skin.

   Verrucae can spread locally by autoinoculation to develop at adjacent sites of viral infection. The spread of the virus is related to the patient’s immune status with more advanced lesions occurring in children and immunocompromised adults. There are several different types of plantar warts. Multiple, shallow, widespread lesions can coalesce to form mosaic warts. Myrmecia are deeply burrowing epidermal lesions that extend far below the skin surface and tend to be very painful. The hypothesis is that the lesions develop secondary to pressure on the skin surface.

   There is no specific definition of recalcitrance but typically, recalcitrant warts are those that persist following several months of conventional treatment. Up to one-third of non-genital warts, especially plantar and periungual warts, become recalcitrant.2 Given that premalignant and malignant skin disorders, including squamous cell carcinoma and verrucous carcinoma, can present with characteristics similar to verrucae, one should perform a punch biopsy for histopathological diagnosis of any suspicious lesions or lesions that fail to respond to standard treatment regimens.

   The treatment of plantar warts tends to be time consuming, costly and painful. Indeed, some modalities can lead to scar tissue formation. There is no single wart treatment that is 100 percent effective. There is a vast array of treatment modalities and the success rates vary significantly. Conventional treatment of warts frequently involves several ablative modalities including debridement, topical keratolytics (salicylic acid) and cantharone. These ablative agents often have the aid of occlusive dressings. Several treatment modalities, including topical medications, oral medication, nutritional supplements, intralesional injections and surgical excision, exist for the treatment of verrucae that fail to respond to conventional treatment.

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