Plantar Warts — SCE Dermatology MCQ

Correct answer: C — Cryotherapy with liquid nitrogen

The correct answer is C, cryotherapy with liquid nitrogen. NICE CKS and BAD guidance on warts and verrucae set topical salicylic acid as first-line self-treatment, applied daily for up to 3 months; when this fails, cryotherapy in primary care is the recommended next step. Cryotherapy works by inducing tissue necrosis and blistering at the dermo-epidermal junction, which triggers a local immune response against the causative HPV-infected keratinocytes. It is typically given at 2 to 3 week intervals for several sessions, and can be combined with continued salicylic acid between freezes. This stepwise approach (salicylic acid, then cryotherapy, then secondary care options) reflects the evidence base and cost-effectiveness data reviewed by NICE. Why the other options are wrong: A. Imiquimod cream: not licensed or recommended as routine next-line therapy for plantar verrucae; its evidence and licensing base is for anogenital warts, not first-line escalation for salicylic acid failure. B. Oral retinoids: reserved for extensive or recalcitrant warts in specialist settings, not indicated as a routine second-line option after topical acid failure. D. Oral antivirals: HPV is not treated with systemic antiviral agents such as aciclovir, as these have no activity against papillomavirus; there is no role for oral antivirals in verruca management. E. Surgical excision: avoided on the weight-bearing sole because it risks painful scarring and recurrence, and is not recommended by BAD or NICE CKS for uncomplicated plantar warts. Key point: after 3 months of unsuccessful topical salicylic acid, cryotherapy with liquid nitrogen is the recommended next-line treatment for plantar warts per NICE CKS and BAD guidance.

Reference: NICE CKS, Warts and verrucae: Management, last revised October 2024, cks.nice.org.uk/topics/warts-verrucae/