The FP diagnosed this patient with palmar warts, which are similar in morphology to plantar warts. Plantar (or palmar) warts are lesions caused by human papillomavirus (HPV) that occur on the soles of the feet and palms of the hands. Plantar warts occur mostly in adolescents and young adults and affect up to 10% of people in these age groups.
Plantar warts usually occur at points of maximum pressure, such as on the heels or over the heads of the metatarsal bones, but may appear anywhere on the plantar surface, including the tips of the toes. A cluster of multiple warts that appear to fuse together is referred to as a mosaic wart. HIV is a risk factor for any type of HPV infection.
Distinguish warts from calluses by noting the skin lines; warts lack skin lines crossing their surface, whereas normal skin lines cross through a callus without any disturbance. Additionally, plantar/palmar warts may have a highly organized mosaic pattern on the surface when examined with a hand lens and have prominent black dots (thrombosed capillaries).
The most common treatments for warts include topical salicylic acid and cryotherapy. Topical salicylic acid preparations are nonscarring, minimally painful, and relatively effective, but require persistent application of medication once a day for weeks to months. Cryotherapy with liquid nitrogen therapy is commonly used, but plantar warts are more resistant than other HPV lesions. The liquid nitrogen is applied to form a freeze ball that covers the lesion and 2 mm of surrounding normal tissue for usually 10 to 20 seconds per treatment. This can be performed as a single long freeze or divided into 2 freezing episodes with thawing in between. This allows for more freeze time in a way that is less painful to the patient.
In this case, the patient chose cryotherapy and arranged for a follow-up appointment in 3 to 4 weeks for a second round.
Photos and text for Photo Rounds Friday courtesy of Richard P. Usatine, MD. This case was adapted from: Mayeaux EJ. Plantar warts. In: Usatine R, Smith M, Mayeaux EJ, et al, eds. Color Atlas of Family Medicine. 2nd ed. New York, NY: McGraw-Hill; 2013:766-770.
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