Despite how common they are, assessing and treating plantar and cutaneous warts can still present challenges. This article explores the key differentials, red flags to watch for and when to refer — plus practical tips to manage these common viral lesions and reduce the risk of recurrence.

Typical features

The classic presentation of a plantar wart includes a firm, nodular, and scaly appearance that is well circumscribed.

The pathognomonic feature is the presence of pinpoint bleeding or thrombosed blood vessels, which become more prominent when examined with dermoscopy. These characteristic blood vessels become even more obvious when the wart is pared back using a curette or disposable scalpel blade, revealing pinpoint bleeding as the thrombosed vessels are exposed.

Warts typically occur in predictable locations including the hands, fingernails, and soles of the feet, particularly affecting young adults to adults. In children, warts may present on other surfaces such as the knees.

It’s worth noting that genital warts in children should raise concerns about potential child abuse, and involvement of child protection services should be considered.

Recognising when a wart is not actually a wart

Differential diagnosis becomes crucial when lesions don’t present with typical wart characteristics.

Red flags include:

• lesions that lack the firm keratin-filled nodular appearance,
• are not responding to treatment,
• occur in unexpected locations, or
• present with unusual features such as ulceration.

Many lesions initially labelled as warts have subsequently been diagnosed as skin cancers following biopsy.

Other conditions to consider in the differential diagnosis include foreign bodies within the soles of feet, benign tumours, and calcification related to underlying skin or systemic diseases.

Viral aetiology and transmission

Warts are caused by human papillomavirus (HPV) and spread through skin-to-skin contact. Common transmission routes include public environments such as swimming pools. For digital warts, transmission often occurs through habits such as nail biting, cuticle picking, or using fingernails to pick at adjacent fingers’ cuticles. Understanding these transmission patterns is essential for both treatment planning and prevention strategies.

First-line treatments

The initial approach should begin with patient education about the viral aetiology and transmission patterns.

For smaller warts (less than 5mm in diameter), liquid nitrogen cryotherapy is an effective first-line treatment.

For larger warts over one centimetre in diameter, particularly those that are deep on the feet, surgical intervention with paring may be warranted.

When paring warts, you can use a 4mm curette (typically reserved for skin cancer management) to gently remove the top layers of skin.

This technique requires careful handling due to the sharp nature of these instruments, but it allows for more effective topical treatment or cryotherapy of the base.

It’s important to warn patients that liquid nitrogen cryotherapy can be very painful during treatment. A double freeze-thaw cycle is recommended, like treating thick actinic keratosis or certain skin cancers, with the area allowed to thaw before treating again in the same session. It does require compliance and pain tolerance from the patient.

Topical treatments: Upton’s paste

A highly effective topical option is Upton’s paste, a traditional dermatological formulation containing six parts salicylic acid to one part trichloroacetic acid, mixed in glycerin to form a stiff paste. Patients can apply this once daily, covering with sticky sports tape between applications and giving the area a gentle scrub between treatments.

Treatment duration varies significantly by location. Digital warts typically require at least four weeks of treatment, while plantar warts may need up to three months.

The extended treatment time reflects the iceberg-like nature of these lesions – what’s visible on the surface is only a fraction of the actual wart tissue beneath.

Managing patient expectations about treatment duration

It’s crucial to warn patients that truncated treatment periods may result in wart recurrence. However, with persistent treatment, the immune system eventually recognises the wart presence, leading to immunological attack and resolution. This explains why adults are generally less susceptible to warts than children – their immune systems have learned to recognise and respond to these viral infections more effectively.

Special considerations for immunosuppressed patients

Cutaneous warts present significant challenges in immunosuppressed patients. These patients may present with widespread warts beyond traditional locations, and standard immunotherapies like imiquimod may be less effective.

Treatments for immunosuppressed patients include contact sensitisation using diphenylcyclopropenone (DPCP), where patients are sensitised to the compound and then treated with dilute solutions applied to warts. However, these treatments are generally less effective, necessitating more destructive methods such as curettage and cautery, or specialised treatments like intralesional bleomycin.

HPV vaccination and cutaneous warts

Despite theoretical crossover between HPV vaccination (designed to prevent cervical cancer) and cutaneous warts, clinical evidence doesn’t support reduced cutaneous wart burden following vaccination. This is because cervical cancer-causing HPV subtypes differ from those causing cutaneous warts, limiting any transferred immunity.

Prevention strategies

Patient education should emphasise several key prevention strategies:

• Avoiding habits that spread warts, such as nail biting or cuticle picking
• Wearing slippers or thongs in communal areas, particularly public swimming pools
• Avoiding sharing baths while warts are being treated
• Minimising skin-to-skin contact during active treatment periods

These simple measures, combined with successful treatment solutions that educate the host immune system, provide the best long-term prevention against wart recurrence.

When to refer to dermatology

Referral to dermatology becomes appropriate when the diagnosis is uncertain, when the lesion doesn’t behave like a typical wart, or when standard GP treatments have failed.

Advanced dermatological treatments

Dermatologists have several additional treatment options. Cantharidin, an extract from blister beetles, creates a painless application that forms blisters, destroying wart tissue while stimulating immune recognition. This treatment typically requires two to three sessions at monthly intervals and has shown good success rates.

For more stubborn cases, intralesional bleomycin is highly effective but requires careful handling protocols due to cytotoxicity. Local anaesthetic can be necessary due to injection pain, but success rates are excellent, often requiring only one to two treatments.

Managing treatment-resistant cases

While some warts may seem treatment-resistant, persistence typically leads to success. Combining in-office treatments with home therapy works well but it’s crucial to set realistic expectations to ensure patient compliance and commitment. Flexibility in application schedules (such as Monday to Friday coverage rather than daily application) can improve compliance while maintaining effectiveness.

Occupational considerations

Treatment planning should consider patients’ occupations and lifestyle requirements. For instance, a professional violinist may need modified treatment approaches to maintain their ability to work, as hand function is critical to their livelihood.

Key takeaways:

• Look for the pathognomonic pinpoint bleeding or thrombosed blood vessels and consider dermoscopy for unclear cases.
• Always maintain a high index of suspicion for alternative diagnoses, particularly skin cancer, when lesions don’t respond to treatment or appear atypical.
• Set clear expectations with patients about treatment duration.
• Use paring techniques for larger warts before applying topical treatments or cryotherapy.
• Upton’s paste (salicylic acid and trichloroacetic acid) combined with proper occlusion provides excellent first-line topical therapy.
• Patient education about transmission patterns and prevention strategies reduces recurrence.
• Consider dermatology referral for treatment-resistant cases, diagnostic uncertainty, or when lesions behave atypically.

Dr Philip Tong is a Sydney-based dermatologist and Founder of DermScreen, a telehealth platform that supports GPs with dermatology-related clinical decision making. He offers nation-wide telehealth services for medical dermatology including acne, eczema and psoriasis through his clinic dermjunction.com.au