General: benign epidermal proliferations caused by various papilloma viruses, common wart is called "verruca vulgaris"


Pathogenesis: dsDNA virus infects and replicates in keratinocytes, presence of virus stimulates epidermal thickening, still a lot to be learned!


HPI: child, young adult who is sexually active, skin lesion that can be painful, single or in groups


Risk factors: HPV infection, immunosuppression, meat handlers have higher incidence


Physical exam: papules/nodules that are flesh-colored, with a corrugated (shaped into alternate ridges and grooves) surface, may scale, will have interrupted skin lines with black puncta, often on hands and fingers


Types of warts: flat (slightly raised, flat-surface, well-marginated, often linear from autoinoculation), plantar (bottom of foot, often with callus), genital (condyloma acuminatum, soft/moist, sessile/pedunculated, cauliflower-like appearance, acetowhitening), types 6 and 11 cause genital warts, types 16 and 18 cause cervical cancers


Differential: callus (can use paring to distinguish; after paring warts will show interrupted skin lines with black puncta), carcinomas (ulcerative, refractory), comedones (smooth top), lichen planus (red-purple), corns (normal skin lines with translucent core), condyloma lata (genital syphilis, darkfield microscopy), seborrheic keratosis, Bowenoid papulosis

Histology: biopsy performed when suspicion for carcinoma is high, shows hyperkeratosis, acanthosis (thickened epidermis), within the granular layer will see vacuolated keratinocytes, koilocytes (large keratinocytes with small pyknotic nuclei surrounded by clear cytoplasm), upward extension of dermal papillae with capillaries


Complications: 35-65% resolve spontaneously within 2 years, main concern is carcinoma, types 16/18 highly associated with cervical and anal carcinoma, need to do pap smears in female patients, consider examining the sexual partner of the patient, *epidermodysplasia verruciformis = rare disease with diffuse, refractory warts due to HPV-5,8 that convert to squamous cell carcinoma*


Treatment: prevention is key; Gardasil vaccine protects against types 6, 11, 16, 18. Other than prevention, treatment aims to destroy keratinocytes infected with virus and can be quite painful. Treatment options = cryotherapy including 1-2 mm beyond margins + second freeze with follow-up useful for all warts; salicylic acid w occlusive tape for common and plantar warts; cantharidin for children (derived from blister beetle!); Retin-A for flat warts; 25% podophyllin resin for genital warts (toxicity, avoid during pregnancy); alternative treatments include 5-FU, interferon, biologics such as imiquimod 


References: AAD Basic Dermatology Curriculum, Dermatology by Bolognia et. al., Lookingbill and Mark's Principles of Dermatology, First Aid USMLE Step 1 2020, First Aid USMLE Step 2 CK