Warts

Benign epidermal proliferations caused by human papillomavirus (HPV) infection of keratinocytes, numerous HPV subtypes correlate with clinical morphology/site.

Transmitted via direct contact or fomites (communal showers/pools for plantar warts), autoinoculation cocommon

Immunocompromised individuals at risk of more extensive/persistent disease.

Classified by morphology/site: common warts (verruca vulgaris: hands, dome-shaped, rough hyperkeratotic surface), plantar warts (verruca plantaris: soles, inward-growing from pressure, may have central black dots = thrombosed capillaries), flat warts (verruca plana: face/hands, smaller, flat-topped, often multiple), genital warts (condylomata acuminata: sexually transmitted, distinct management pathway).

Common: firm, rough-surfaced papules, often on hands/fingers, may coalesce ("mosaic warts").

Plantar: tender with pressure (walking), disrupts normal skin lines (distinguishes from callus which preserves skin lines), central black puncta (thrombosed vessels) often visible when pared.

Flat: smooth, slightly elevated, skin-colored/light brown, often numerous, Koebnerization along scratch lines.

Clinical: characteristic appearance usually sufficient.

Paring: reveals thrombosed capillaries (black dots) in warts vs. absence in corns/calluses, and disruption of skin lines.

Biopsy: rarely needed, reserved for diagnostic uncertainty, atypical/pigmented lesions, or non-healing/suspicious lesions (exclude malignancy, particularly in immunocompromised or elderly).

Differentials: corns/calluses (preserve normal skin lines, painful with direct pressure rather than lateral compression), molluscum contagiosum (umbilicated, different virus), seborrheic keratosis, actinic keratosis, squamous cell carcinoma (consider if atypical, rapidly growing, non-healing, especially immunosuppressed/elderly; biopsy if any doubt).

Note: many warts resolve spontaneously within 1-2 years (especially in children) without treatment: watchful waiting is a reasonable first option, particularly for asymptomatic lesions in children.

• Topical salicylic acid (various strengths, 15-50%): first-line, applied regularly (often daily) with paring of dead tissue between applications; requires weeks-months of consistent use, most evidence-based OTC option

• Cryotherapy (liquid nitrogen): effective, typically repeated every 2-3 weeks, several sessions often needed; some discomfort/blistering expected

• Combination salicylic acid + cryotherapy: superior to either alone for resistant warts

• Duct tape occlusion: adjunct/alternative, modest evidence, low-risk option

• Resistant/extensive warts: topical imiquimod (immune modulator), intralesional immunotherapy, laser therapy, or topical/intralesional bleomycin (specialist dermatology)

• Plantar warts: paring + salicylic acid/cryotherapy; padding/offloading for symptomatic relief during treatment

• Immunocompromised patients: often more extensive/persistent, may require prolonged/combination treatment, lower threshold for dermatology referral

• Genital warts: separate management pathway; podophyllotoxin, imiquimod, or cryotherapy at genital sites; STI screening and partner notification; note HPV vaccination is preventive (not therapeutic for established warts) and relevant for future risk reduction counseling

Referral: dermatology for diagnostic uncertainty, extensive/resistant disease, immunocompromised patients, or any lesion with atypical/concerning features warranting biopsy.