INTRODUCTION
Verruca (plantar warts) are a common problem caused by the human papilloma virus (HPV) that can be irritating and painful. Current treatment of verruca is limited to traditional therapies that are quantified by two distinct mechanistic activities–either destructive or immunomodulating.1 Destructive therapies can be further segregated into those that are topical pharmacologic in nature (eg, salicylic acid, monochloroacetic acid) or physical (eg, surgery, cryotherapy). Susceptibility of HPV to antivirals is not possible as HPV is not conducive to being cultured in vitro.
An initial Cochrane Database review of nongenital wart treatments was performed in 2006 in an effort to assess the quality of existing evidence.2 The authors concluded that there was a lack of evidence to substantiate treatment with topical agents. Specifically, most evidence supported the use of topical treatments that contained salicylic acid. This review was updated in 2011 with similar recommendations after reviewing 26 new additional studies.3 An alternate systematic review of 15 trials was performed in 2012, analyzing the efficacy of systemic treatment of cutaneous warts, including levamisole, homeopathy, zinc sulphate, and cimetidine. While levamisole and homeopathy were found ineffective, zinc sulphate and cimetidine evidence was also limited due to methodological flaw and inconclusive efficacy, respectively.4
Acyclovir is a synthetic purine nucleoside analogue with activity against herpes simplex virus type 1 (HSV-1), 2 (HSV-2), and varicella-zoster virus (VZV). Acyclovir uses viral thymidine kinase to convert to acyclovir monophosphate, a nucleotide analogue that is eventually converted to its active form of acyclovir triphosphate. Through this mechanism of utilizing viral thymidine
kinase to convert to its active form, acyclovir specifically targets viral DNA, preventing replication of the herpes virus in the host. A dose of 800mg every 4 hours for 7 to 10 days is commonly used for acute treatment of herpes zoster (shingles).5 Early reports have indicated no difference in the treatment of verruca with topical acyclovir versus traditional therapy.6
There remains a paucity of data to support the use of oral acyclovir which achieves systematic concentrations in the body, for the treatment of verruca.7 We report a case where verruca incidentally resolved in a patient receiving acyclovir for the treatment of shingles.
CASE
A 49 year-old Caucasian female with non-significant past medical history presented to the podiatry clinic in March 2014 for treatment of verruca. Upon examination, two 3mm and three 2mm verrucae were identified on the second medial and metatarsal head of the left foot. The patient complained of discomfort and a pain level of 5/10. Debridement was performed and monochloroacetic acid was applied to affected areas. Further debridement and monochloroacetic acid application were performed at each of the six subsequent visits over the next seven months, with the last treatment in October 2014. The pain subsided to a score of 3/10, however the size of the verrucae remained unchanged.
Approximately one month later, the patient presented to her primary care provider with a visible rash on the base of her neck and right shoulder with visible blisters that started four days prior. A diagnosis of herpes zoster was given and the
