Chapter 117: Flat Warts

Patient Story

A 16-year-old girl presents with multiple flat lesions on her forehead (Figure 117-1). 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 characterized as flat or slightly elevated flesh-colored papules. They may be smooth or slightly hyperkeratotic. They range in size from 1 to 5 mm or more, and numbers range from a few to hundreds of lesions, which may become grouped or confluent. They occur most commonly on the face, hands, and shins. They may appear in a linear distribution as a result of scratching, shaving, or trauma (Koebner phenomenon) (Figures 117-2 and 117-3).

Synonyms

Plane warts, verruca plana, verruca plana juvenilis, plane warts.

Epidemiology

• Flat warts (verruca plana) are most commonly found in children and young adults (Figures 117-1 to 117-3).

• Flat warts are the least common variety of wart, but are generally numerous on an individual.¹

• Flat warts are usually caused by human papillomavirus (HPV) types 3, 10, 28, and 29.²

Etiology and Pathophysiology

• Like all warts, flat warts are caused by HPV.²

• Flat warts may spread in a linear pattern secondary to spread by scratching or trauma, such as shaving (Figure 117-2 and 117-3).

• Flat warts present a special treatment problem because they persist for a long time, they are generally located in cosmetically important areas, and they are resistant to therapy.

Risk Factors

• Shaving next to infected areas (Figures 117-2 and 117-3).

• HIV infection or other types of immunosuppression.

Diagnosis

Clinical Features

• Multiple small, flat-topped papules that may be pink, light brown, or light yellow colored. They may be polygonal in shape (Figure 117-4).