Warts and verrucae
Exam Tips
- If skin lines run through a lesion and there are no punctate bleeding points on paring, think callus/corn rather than verruca.
- Black dots in plantar warts are thrombosed capillaries, a classic OSCE discriminator.
- In children with asymptomatic lesions, explaining natural resolution and avoiding painful procedures is often best practice.
- Red flags for urgent reassessment/referral: atypical pigmentation, ulceration, rapid growth, persistent inflammation, immunosuppression, or diagnostic uncertainty.
- For UK exams, remember: non-facial first-line is usually topical salicylic acid; cryotherapy is selective and less useful for plantar disease.
Definition
Cutaneous warts are benign hyperkeratotic epidermal lesions caused by infection of keratinocytes with human papillomavirus (HPV), usually acquired through direct contact or contaminated surfaces. A verruca is a plantar wart on the sole of the foot, often painful due to pressure and overlying callus. In UK primary care, diagnosis is usually clinical and many lesions resolve spontaneously without active treatment.
Pathophysiology
HPV enters through microscopic skin breaks and infects basal keratinocytes, promoting epidermal proliferation and delayed keratinocyte maturation. This produces acanthosis, papillomatosis, and hyperkeratosis, giving the rough verrucous surface. On weight-bearing skin (plantar lesions), inward growth plus pressure causes pain; punctate black dots represent thrombosed capillary loops. Autoinoculation (for example from picking or shaving) and Koebnerization at trauma sites explain spread and clustering (including mosaic plantar warts). Immunosuppression reduces viral clearance, so lesions can be larger, more numerous, and treatment-resistant.
Risk Factors
- School-age and adolescent exposure (peak prevalence in childhood/early adulthood)
- Skin barrier disruption, eczema, microtrauma, or macerated/wet skin
- Frequent barefoot use of communal wet floors (swimming pools, shower rooms)
- Nail biting/picking and shaving (autoinoculation)
- Occupational handling of meat or fish
- Frequent water immersion (for example dishwashing, swimming)
- Immunosuppression (including post-transplant states)
Clinical Features
Symptoms
- Often asymptomatic
- Localized tenderness or pain, especially plantar lesions on weight-bearing areas
- Cosmetic concern/embarrassment
- Pain around nail folds with periungual disease
Signs
- Common warts: firm, raised, rough keratotic papules (often fingers, knuckles, knees)
- Plantar/palmar warts: endophytic hyperkeratotic lesions with punctate black dots (thrombosed capillaries)
- Periungual warts: peri-nail keratotic growths with possible nail dystrophy
- Plane warts: flat-topped, skin-coloured or grey-yellow papules (face, backs of hands, shins)
- Filiform warts: finger-like fronds/pedunculated lesions (face/neck)
- Mosaic warts: coalescent plaques of plantar/palmar warts
- See DermNet/PCDS clinical image libraries for morphology comparison in exams
Investigations
Management
Lifestyle Modifications
- For many patients (especially children), watchful waiting is appropriate as spontaneous resolution is common
- Avoid picking, scratching, nail biting, and shaving across lesions to reduce spread
- Keep feet dry, use footwear in communal wet areas, and avoid sharing pumice stones/towels
- For painful plantar lesions, careful regular paring of overlying callus can improve comfort; avoid damaging surrounding skin
- Advise review if lesions change, enlarge, bleed, become persistently painful, or fail to respond
Pharmacological Treatment
Topical keratolytic
- Salicylic acid topical preparations 12-26% (for example paints/gels/collodions) applied once daily for up to 12 weeks
- For plane warts on backs of hands, consider lower strength salicylic acid (<=17%) to reduce scarring risk
First-line for most non-facial cutaneous warts, including younger children when treatment is needed. Counsel that improvement is slow and local irritation is common. Avoid use on face, anogenital skin, inflamed/broken skin, and use caution in diabetes, neuropathy, or poor peripheral circulation due to risk of tissue injury.
Surgical / Interventional
- Liquid nitrogen cryotherapy every 2-4 weeks (typical freeze 5-10 seconds for less aggressive regimens), up to about 6 sessions
- Combination approach: continue topical salicylic acid between cryotherapy sessions once post-freeze scabbing settles
- Do not routinely treat facial warts in primary care; refer to dermatology if intervention is required
- Avoid cryotherapy in younger children who are unlikely to tolerate pain; plantar warts are often less responsive than other sites
Complications
- Autoinoculation and spread to close contacts
- Secondary local infection
- Pain-related gait change with plantar disease (possible secondary knee/hip discomfort)
- Psychosocial impact (stigma, school/sport avoidance)
- Periungual disease causing nail dystrophy/destruction
- Treatment adverse effects: blistering, pain, dyspigmentation, scarring
- Rare malignant transformation (higher concern in immunosuppressed patients and epidermodysplasia verruciformis)
Prognosis
Variable; many clear spontaneously. In children, approximately 25% resolve within months, around 50% within 1 year, about two-thirds within 2 years, and most by 5 years. Adult clearance is typically slower (often several years), and immunosuppressed patients may have persistent, extensive, treatment-refractory lesions.
Sources & References
✅NICE Guidelines(1)
- Warts and verrucae[overview]