Chapter 138: Flat Warts

PATIENT STORY

A 16-year-old girl presents with multiple flat lesions on her forehead (Figure 138-1). It started with just a few lesions but has spread over the past 3 months. She is diagnosed with flat warts, and topical imiquimod is prescribed as the initial treatment.

INTRODUCTION

Flat warts are one of the three cutaneous manifestations of warts caused by human papillomavirus (HPV). Flat warts are characterized as flat or slightly elevated flesh-colored papules. Ranging from a few to hundreds of lesions, these warts occur most commonly on the face, hands, and shins and can cause significant patient distress (Figure 138-2).

SYNONYMS

Plane warts, verruca plana, verruca plana juvenilis.

EPIDEMIOLOGY

• Flat warts (verruca plana) are most commonly found in children and young adults (Figures 138-1, 138-2, 138-3, 138-4, 138-5).

• Flat warts are the least common variety of wart but are generally numerous on an individual.¹ They represent up to 4% of all cutaneous warts, while common and plantar warts represent 71% and 34%, respectively.²

• Flat warts are usually caused by HPV types 3, 10, 28, and 29.³

ETIOLOGY AND PATHOPHYSIOLOGY

• Like all warts, flat warts are caused by HPV.³ Infection with HPV can occur by coming in direct contact with intact, macerated, or traumatized skin.

• Flat warts may spread in a linear pattern secondary to spread by scratching or trauma, such as shaving (Koebner phenomenon) (Figure 138-2).

• Flat warts ...