Dermatology MCQ - Viral Infections - Cutaneous warts

A 10-year-old boy presents with multiple, firm, hyperkeratotic papules with a rough, cauliflower-like surface on his fingers and knees. The lesions are asymptomatic but cosmetically concerning. Which of the following is the most appropriate first-line treatment and the underlying viral pathogen?

A) Cryotherapy with liquid nitrogen; human papillomavirus (HPV)
B) Oral acyclovir; herpes simplex virus (HSV)
C) Topical corticosteroids; human polyomavirus
D) Oral fluconazole; Candida albicans
E) Surgical excision; molluscum contagiosum virus

Correct Answer: A) Cryotherapy with liquid nitrogen; human papillomavirus (HPV)

Explanation

This presentation is classic for common warts (verruca vulgaris), caused by human papillomavirus (HPV).

Key Clinical Features of Cutaneous Warts:

• Appearance: Firm, hyperkeratotic, papulonodular lesions with a rough, verrucous (cauliflower-like) surface. They may have black dots (thrombosed capillaries) on paring.

• Distribution: Common on hands, fingers, knees, and other trauma-prone sites.

• Types:

  • Verruca vulgaris: Common warts (as described).

  • Verruca plantaris: Plantar warts (on soles).

  • Verruca plana: Flat warts (smooth, flat-topped papules).

• Cause: Human papillomavirus (HPV) types 1, 2, 4, 27, 57 (among others). HPV infects keratinocytes, causing hyperproliferation and hyperkeratosis.

First-Line Treatment:

• Cryotherapy with liquid nitrogen: Freezes and destroys the infected tissue, stimulating an immune response. It is effective, quick, and widely available.

• Other options:

  • Topical salicylic acid: Over-the-counter keratolytic treatment.

  • Topical imiquimod: Immune response modifier (useful for recalcitrant warts).

  • Electrosurgery, laser therapy, or topical 5-fluorouracil for resistant cases.

Why Not the Other Options?

• (B) Oral acyclovir; HSV: Acyclovir targets herpesviruses (e.g., HSV, VZV), not HPV. Herpes lesions are vesicular, not hyperkeratotic.

• (C) Topical corticosteroids; human polyomavirus: Corticosteroids are anti-inflammatory and used for eczematous or autoimmune conditions, not viral warts. Polyomaviruses cause trichodysplasia spinulosa, not common warts.

• (D) Oral fluconazole; Candida albicans: Antifungals treat fungal infections (e.g., tinea, candidiasis), which present as scaly plaques or pustules, not verrucous papules.

• (E) Surgical excision; molluscum contagiosum: Molluscum causes dome-shaped, umbilicated papules, not hyperkeratotic lesions. Surgical excision is not first-line for warts due to scarring risk.

Pathogenesis:

• HPV enters through microabrasions in the skin, infecting basal keratinocytes. Viral E6 and E7 proteins disrupt cell cycle regulation, leading to uncontrolled proliferation and hyperkeratosis.

Prognosis:
Most warts resolve spontaneously within 1-2 years due to immune recognition. Treatment accelerates clearance and reduces transmission.

Note: HPV vaccines (e.g., Gardasil 9) protect against genital HPV types but not against common cutaneous wart types.