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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.

FIGURE 117-1

Flat warts on a patient’s forehead. (Used with permission from Richard P. Usatine, MD.)

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).

FIGURE 117-2

Flat warts just above the knee of a young woman. Notice the linear distribution probably resulting from spread by shaving (Koebner phenomenon). (Used with permission from Richard P. Usatine, MD.)

FIGURE 117-3

Flat warts on the hand of a child. Note the linear distribution, which is probably the result of scratching or minor trauma (Koebner phenomenon). (Used with permission from Richard P. Usatine, MD.)

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).

FIGURE 117-4

Close-up of a flat wart. Note typical small, flat-topped ...

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