Plantar Wart

A plantar wart, also known as verruca myrmecia or verruca plantaris, is a common dermatological condition characterised by a wart occurring on the bottom of the foot or toes. The condition primarily falls under the specialties of dermatology and podiatry. Plantar warts are typically skin-coloured lesions that can be painful, especially when subjected to pressure, making walking difficult.

Signs and Symptoms

Plantar warts are generally similar in colour to the surrounding skin and often exhibit small black dots on their surfaces. These warts can appear singly or in clusters. They are commonly painful under pressure, complicating mobility.

Cause

Plantar warts are benign epithelial tumours caused by human papillomavirus (HPV) types 1, 2, 4, 60, or 63, among others. The virus infects compromised skin through direct contact, often entering through minor abrasions. The incubation period can vary, and the warts may not become visible for several weeks or months. The pressure on the sole of the foot can push the wart inward, covered by a layer of hard skin, potentially causing pain if untreated. Warts can spread through autoinoculation or contaminated surfaces.

Diagnosis

Diagnosis is typically based on symptoms and visual examination. Plantar warts usually appear as small lesions resembling cauliflower, with tiny black petechiae in the centre. They are often painful when standing or walking and can be differentiated from calluses by observing the disruption of skin striations. Unlike calluses, plantar warts are painful when pressure is applied from the sides rather than directly.

Prevention

HPV spreads through direct and indirect contact with contaminated surfaces. Preventive measures include avoiding direct contact with communal showers, changing rooms, and not sharing shoes or towels. Wearing flip-flops in communal areas and covering warts while swimming can help reduce the spread. It is important to note that HPV vaccines such as Gardasil and Cervarix do not provide protection against the strains that cause plantar warts.

Treatment

Treatment is typically required only if the wart is causing symptoms. Various treatments have been found effective:

Medications

• Salicylic Acid: Both over-the-counter and prescription formulations are available. The treatment involves keratolysis, peeling away dead skin cells. A 12-week treatment can lead to complete clearance in 10-15% of cases.
• Formic Acid: Applied topically, it causes the body to reject the wart.
• Fluorouracil Cream: A chemotherapy agent used for resistant warts, it blocks viral DNA and RNA production.
• Bleomycin: Injected into deep warts, this chemotherapy drug destroys viral DNA or RNA but can have severe side effects.

Surgery

• Cryotherapy: Liquid nitrogen is used to freeze and destroy wart tissue.
• Electrodesiccation and Surgical Excision: These methods may produce scarring.
• Laser Surgery: Considered a last resort due to expense and pain.
• Cauterisation: Effective but risks scarring and recurrence.

Intralesional immunotherapy, involving injections of antigens, is now recommended as a second-line therapy, aiming to trigger an immune response against the wart virus.

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Self-assessment MCQs (single best answer)

What is another name for a plantar wart?

What virus is responsible for causing plantar warts?

Which of the following HPV types is NOT typically associated with plantar warts?

What is a distinguishing feature of plantar warts compared to calluses?

Which treatment involves the use of liquid nitrogen to destroy wart tissue?

What preventive measure can help reduce the spread of plantar warts in communal shower areas?

Which medication is a chemotherapy agent used for resistant plantar warts?

What is the main reason plantar warts can be painful?

Which type of surgery is considered a last resort due to expense and pain for treating plantar warts?

Which treatment involves injecting antigens to trigger an immune response against the wart virus?