Chapter 122: 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.

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

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

• Vesicles, pustules, honey-colored (see Figure 122-1), brown or dark crusts, erythematous erosions (Figure 122-3), ulcers in ecthyma (Figure 122-4), bullae in bullous impetigo (Figures 122-5, 122-6, 122-7).