Twenty-seven patients with periungual warts, who were treated from 2007 through 2010 in Dongguk University Ilsan Hospital, were included in this study. Some lesions were treated with DPCPi alone, while others employed multiple therapies with DPCPi after cryotherapy and/or pulsed-dye laser were initially performed.

All recruited subjects were treated with DPCPi. While other treatment modalities including cryotherapy and/or pulsed-dye laser were employed initially in some cases, DPCPi was the last method used to complete the treatment. The DPCP solution of concentration 0.1% (for adults) and 0.05% (for pediatric patients) were applied on the upper inner arm to induce sensitization. It was confirmed to have occurred on the week following when the application site showed eczematous conditions, which were represented by an itch, erythema and/or mild oozing. Once a patient was sensitized, DPCP of an appropriate concentration starting from 0.1%, which was gradually increased up to 2% until a mild eczematous reaction was noticed, was applied onto the lesions weekly until all lesions cleared. The concentration of DPCP was adjusted depending on the severity of the inflammatory reaction from the previous application. If the reactions were severe enough to have bullae or severe oozing, the concentration was lowered. The concentration was elevated when the reaction from the previous application was too weak to produce desired results. The desired target concentration was the initial point when erythema, mild itch and/or mild oozing was observed.

We assessed the results of the treatment as 'success' or 'failure.' A 'success' was clinically defined as when all lesions were completely cleared, and 'failure' was considered in one of the following four conditions: (i) if a patient had not been sensitized; (ii) if a proper reaction had not occurred on the wart lesions that were treated with DPCPi for 3 consecutive weeks in a sensitized patient; (iii) if clinical improvement had not been observed for 3 consecutive weeks, although a proper reaction of DPCP application had occurred; and (iv) if there were severe adverse reactions, including generalized eruptions and intolerable itch.

We grouped the lesions into three different types, according to the location: proximal nail fold, lateral nail fold and hyponychium types (Fig. 1A, C, E). Total success rate was assessed, both by the subject and individual wart lesion. In addition, group success rate and treatment period were investigated to compare inter-group differences. Success rate and treatment period according to disease duration were also investigated. Adverse side-effects including generalized itch and/or eczematous eruptions during the treatment period and the recurrence rate after six months of successful treatment were monitored.

We conducted a telephone questionnaire for those who received multiple therapies. Pain and satisfaction of each treatment were evaluated in the questionnaire, which used the visual analogue scale (VAS) score. We also investigated the preferred treatment with the question, 'What would be your choice of treatment be if you had a newly occurred wart lesion and why?'

Statistical analysis was performed to compare success rates between locations and disease duration, utilizing Fisher's exact test. Mann-Whitney U test was utilized to analyze the questionnaire results and to compare treatment periods between the location and disease duration. p<0.05 was considered to be significant.

Of the 27 patients, 14 were male and 13 were female. The mean age was 10.9 years (ranging from 1 to 38). The total number of individual lesions was 66, with 37 proximal-nail-fold lesions, 15 lateral-nail-fold lesions and 14 hyponychium lesions. Mean number of lesions per subject was 2.44 (varying from 1 to 6).

Total success rate, assessed by each subject, was 85% (23/27 subjects), and it was 91% (60/66 lesions) when evaluated by individual lesions (Fig. 1). Among the 23 patients who were treated successfully, 11 were treated with DPCPi only and the others with multiple therapies (Fig. 2). The success rate for proximal nail fold type (95%) was higher than those of other locations: 87% for lateral nail fold and 86% for hyponychium (Fig. 3A). Success rates decreased as the disease duration increased: 100% (5/5, less than 6 months), 89.5% (17/19, 6 to 12 months) and 33.3% (1/3, older than 12 months) (Fig. 3B). Statistical significance was not noted when comparing the success rates of different locations and disease durations. Treatment periods, according to the location, were 12.8, 21.7 and 23.7 weeks for proximal nail fold, lateral nail fold and hyponychium lesions, respectively (Fig. 3C). There were no statistically significant differences in the treatment periods for the different locations. Treatment periods according to disease duration were 7.8, 17.7 and 54 weeks for less than 6 months, 6 to 12 months and over 12 months, respectively. The treatment period increased as the disease duration increased with statistical significance (Fig. 3D). There were 4 treatment failures for the following reasons: two were not sensitized and the other two did not show proper reactions on the wart lesions that were treated with DPCPi, although sensitization was achieved (Fig. 2). We had an aggravated itch that was relieved by systemic antihistamine in 17% (4/23 patients). Significant adverse reactions such as severe widespread eczematous eruption or intolerable urticaria were not observed. Recurrence was observed in one of the 23 patients, with a successful treatment 6 months after the clearance.

Among the 27 patients, a questionnaire was performed for 12 subjects who received multiple therapies. Number of patients treated with other therapies, in addition to DPCPi, was 4 for cryotherapy, 5 for pulsed-dye laser and 3 for both cryotherapy and pulsed-dye laser (Fig. 2). Mean VAS of pain for DPCPi was 0, whereas cryotherapy and pulsed-dye laser showed 8.57 and 8.87, respectively (Fig. 4A). Mean VAS score of satisfaction for DPCPi (8.3) was significantly higher than that for cryotherapy (5.6) and pulsed-dye laser (4.3) (Fig. 4A). There were 11 of 12 patients who chose DPCPi as the treatment of choice if a newly occurred wart lesion (Fig. 4B). Of these 11, 10 patients preferred DPCPi for the painless application and 1 for the satisfactory improvement.