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Impetigo

PATIENT STORIES

A young woman presented to the office with a 3-day history of an uncomfortable rash on her lip and chin (Figure 122-1). She denied any trauma or previous history of oral herpes. This case of impetigo resolved quickly with oral cephalexin.

FIGURE 122-1

Typical honey-crusted plaque on the lip of an adult with impetigo. (Reproduced with permission from Richard P. Usatine, MD.)

An 11-year-old child presented with a 5-day history of a skin lesion that started after a hiking trip (Figure 122-2). This episode of bullous impetigo was found to be secondary to methicillin-resistant Staphylococcus aureus (MRSA). The lesion was rapidly progressive and was developing a surrounding cellulitis. She was admitted to a hospital and treated with intravenous clindamycin with good results.1

FIGURE 122-2

Bullous impetigo secondary to methicillin-resistant Staphylococcus aureus (MRSA) on the leg of an 11-year-old child. Note the surrounding cellulitis. (Reproduced with permission from Studdiford J, Stonehouse A. Bullous eruption on the posterior thigh 1. J Fam Pract. 2005;54:1041-1044. Frontline Medical Communications, Inc.)

INTRODUCTION

Impetigo is the most superficial of bacterial skin infections. It causes honey crusts, bullae, and erosions.

EPIDEMIOLOGY

  • Most frequent in children ages 2 to 6 years, but it can be seen in patients of any age.

  • Common among homeless people living on the streets.

  • Seen often in third world countries in persons living without easy access to clean water and soap.

  • Contagious and can be spread within a household.

ETIOLOGY AND PATHOPHYSIOLOGY

  • Impetigo is caused by Staphylococcus aureus (S. aureus) and/or a β-hemolytic Streptococcus (S. pyogenes).2

  • Bullous impetigo is almost always caused by S. aureus and is less common than the typical crusted impetigo.

  • Impetigo may occur after minor skin injury, such as an insect bite, abrasion, or dermatitis.

DIAGNOSIS

CLINICAL FEATURES

FIGURE 122-3

Widespread impetigo with honey-crusted erythematous lesions on the back of a 7-year-old child. (Reproduced with permission from Richard P. Usatine, MD.)

FIGURE 122-4

Impetigo on the face and hand of a homeless man. Note the ecthyma (ulcerated impetigo) on the dorsum of the hand. (Reproduced with permission from Richard P. Usatine, MD.)

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