Verruca (Warts)
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Direct answer
Warts (verrucae) are benign epidermal proliferations induced by human papillomavirus (HPV) infecting basal keratinocytes through micro-abrasions, spread by auto-inoculation along Koebner lines of trauma. Clinical forms map to HPV types: deep palmoplantar myrmecia (HPV-1), common verruca vulgaris of hands (HPV-2 and 4), plane warts of face and forearms (HPV-3 and 10), filiform warts on the face, and anogenital condylomata acuminata (predominantly HPV-6 and 11, benign types; 16 and 18 are the oncogenic ones covered by vaccine). Most cutaneous warts in immunocompetent individuals regress spontaneously within about two years, so observation is legitimate; active first-line therapy is keratolytic salicylic acid 15-20% with daily paring, or cryotherapy with liquid nitrogen every 2-3 weeks. Anogenital warts additionally respond to imiquimod 5% or podophyllotoxin, and quadrivalent vaccination prevents the causative types.
What you must remember
- HPV type map to memorise: 1 — deep myrmecia plantar warts (painful, "walking on a pebble"); 2, 4 — common warts; 3, 10 — plane warts; 6, 11 — anogenital and laryngeal papillomas (about 90% of genital warts); 16, 18 — high-risk oncogenic; 5, 8 — epidermodysplasia verruciformis.
- Morphology set: verruca vulgaris (fungating dome with thrombosed capillary dots), plane warts (flat-topped, polygonal, flesh-coloured, Koebnerise in scratch lines), filiform (digitating, eyelids and lips), plantar (endophytic, tender, pared surface shows pinpoint bleeding), mosaic plaques.
- Signs that prove wart at the bedside: absence of skin lines (fingerprint lines detour around the lesion) and pinpoint bleeding after paring — versus corn, which has a hard translucent core and preserved lines.
- Treatment ladder for cutaneous warts: salicylic acid 15-20% under occlusion with weekly paring (best trial evidence), cryotherapy 10-30 seconds every 2-3 weeks (4 sessions before declaring failure), cantharidin, imiquimod, pulsed-dye laser; "do nothing" for young children — about half resolve within a year and most within two.
- Anogenital warts: podophyllotoxin 0.5% solution self-applied twice daily for 3 days a week for up to 4 weeks, imiquimod 5% three times weekly, cryotherapy; never podophyllin in pregnancy; screen for other STIs per NACO practice.
- Special warnings: giant condyloma of Buschke-Loewenstein — a locally destructive, non-metastasing verrucous carcinoma of HPV-6/11; Heck disease (focal epithelial hyperplasia, HPV-13/32) — cobblestone lip papules in children of certain communities; numerous or refractory warts suggest HIV or iatrogenic immunosuppression.
- Epidermodysplasia verruciformis: autosomal recessive susceptibility (EVER1/EVER2 genes) to HPV-5/8; plane-wart-like lesions and pityriasis versicolor-like macules that transform into squamous cell carcinoma on sun-exposed skin — lifetime photoprotection.
- Immunosuppression rule: transplant recipients and HIV patients develop multiple, therapy-resistant warts with elevated SCC risk — treat early, biopsy anything atypical.
Choosing between waiting and treating
A healthy 8-year-old with three common warts on the fingers needs, first of all, a decision about whether to treat at all: two-thirds of childhood warts vanish within two years, and any destructive therapy in a frightened child carries more cost than benefit. If the child is troubled, home salicylic acid 17% after soaking and paring is the evidence-based start. A 45-year-old diabetic with a painful plantar wart is different: paring relief, salicylic acid, and cryotherapy are weighed against neuropathy and ulcer risk in the diabetic foot, and biopsy enters early if the lesion fails two therapies, because verrucous carcinoma hides inside "stubborn warts".
The anogenital wart consultation runs on a second algorithm. External condylomata respond to patient-applied podophyllotoxin or imiquimod; pregnancy forbids the cytotoxic options and favours cryotherapy; urethral meatal and extensive lesions need procedural removal. Every case earns an HIV and syphilis test and partner advice in Indian STI practice. And the unanswered question — "will it come back?" — deserves honesty: clearance rates are high but recurrence within months is common because HPV persists in surrounding clinically normal skin.
How the exam chooses its wart question
The commonest format is the type-number match: painful deep plantar wart — HPV-1; flat facial warts in a child — HPV-3/10; genital wart — HPV-6/11; cancer association — 16/18. The second format is bedside differentiation of plantar wart from corn: skin lines lost and pinpoint bleeding on paring favour the wart. Third is therapy hierarchy, where salicylic acid and cryotherapy outrank unproven folk remedies and where the answer to "recalcitrant warts in a young adult" is to test for HIV. The viva examiner's curveball is usually epidermodysplasia verruciformis — the genodermatosis of HPV-5/8 with malignant transformation in sun-exposed skin.
Frequently asked questions
Which HPV type causes deep painful plantar myrmecia warts?
HPV-1, producing endophytic, deeply burrowing warts that feel like walking on a pebble.
How is a plantar wart differentiated from a corn?
A wart loses skin-line markings, shows black thrombosed capillary dots and pinpoint bleeding on paring, whereas a corn has a hard translucent core with preserved skin lines.
What is first-line treatment for common cutaneous warts?
Salicylic acid 15-20% with paring under occlusion, or cryotherapy with liquid nitrogen every 2-3 weeks; watchful waiting is reasonable in young children.
Which topical agents are used for anogenital warts?
Patient-applied podophyllotoxin 0.5% or imiquimod 5%, plus clinic cryotherapy; podophyllin and podophyllotoxin are contraindicated in pregnancy.
What is epidermodysplasia verruciformis?
An autosomal recessive defect of cell-mediated HPV control (EVER1/EVER2) allowing HPV-5/8 lesions that progress to squamous cell carcinoma in sun-exposed skin.