Warts or verrucae are skin lesions caused by infection by human papillomavirus (HPV).
Warts come in many shapes and sizes. The most common is the hyperkeratotic, verrucous papule on the hands or feet of a child. Flat warts are slightly raised, flat papules or small plaques. Occasionally, they may resemble nevi. Many warts are exophytic (stick out), but lesions on the soles are usually endophytic (extend into the skin) because of the constant pressure. Warts commonly occur about the nails, especially in children who bite or pick their nails. Warts do not show fingerprints, in contrast to calluses.
Darker-skinned patients get warts less commonly which is fortunate given that cryotherapy easily induces white spots after therapy.
For decades, the black dots characteristically seen in warts were thought to be thrombosed capillaries. This has turned out not to be the case. They actually represent intracorneal hemorrhages. One should note that paring removes them before the dermis is reached.
If located on the sole, be sure to confirm the diagnosis by paring. A wart has black dots; a corn has a clear center. Verrucous lesions that resist treatment should be biopsied. Occasionally a squamous cell carcinoma or even an amelanotic melanoma may be found. Subungual lesions in an adult should raise particular concern and prompt biopsy sooner rather than later to rule out squamous cell carcinoma).
No treatment is needed for these benign lesions. 2/3 of common warts resolve within 24 months and observations should be considered before embarking on treatment. However, they are contagious, both to the patient and to others. Some practitioners have patients apply clear nail polish every day or so to the warts to prevent spread.
The mainstay of treatment is cryotherapy (freezing) performed every 2-3 weeks. A single 10 second freeze seems optimum, based upon studies. A second freeze-thaw added benefit only for plantar warts in one study. Waiting more than 3 weeks between treatments allows the wart time to grow back. Two weeks between treatments seems to be optimum for most patients. However, one study of external genital warts found that double freeze-thaw every 7-8 days required fewer sessions and cleared quicker than every 14-21 days.
It is not unusual for the patient to need 6-10 treatments in order to clear the warts. Thus, the patient should be told that one treatment rarely does it--multiple treatments are needed.
A 2022 review found the following intralesional modalities were identified (median cure rates): vitamin D3 (80%), bleomycin (74%), 5-fluorouracil (59%), Candida antigen (66%), zinc sulfate (70%), and purified protein derivative (67%).
Occluding a digital wart with duct tape for 6.5 days to make it "mushy" (and some theorize better allowing the immune system to recognize the wart) can be effective. On the seventh day, the duct tape is removed and the wart pared down and allowed to dry. The tape is then reapplied. Repeat as necessary as long as progress is being made.
The CO2 or pulsed dye laser is often employed in recalcitrant cases.
When the immune system finally wins and kills the wart, it dries up, turns brown/black and falls off.
Warts may be spread through autoinnoculation.
A subungual wart. For longstanding lesions, especially in older patients, a biopsy to rule out squamous cell carcinoma may be in order.
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