Chapter 99: Impetigo

Patient Stories

A young boy presented to the office with a 3-day history of an untreated skin infection on his ear (Figure 99-1). His mother states that he has had white spots on his face for the past year but does not know how the ear infection started. The clinician noted honey crusts and purulent drainage from the lower pinna and pityriasis alba on the face. The child was not febrile and was behaving normally. Oral cephalexin was prescribed for the impetigo and 1 percent hydrocortisone ointment was given for the p. alba. Washing and hygiene issues were discussed to avoid spreading the infection within the household. During the 1-week follow-up appointment the impetigo was gone and the p. alba was improving.

An 11-year-old-child presented with a 5-day history of a skin lesion that started after a hiking trip (Figure 99-2). 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 developing 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 S. aureus and/or group A β-hemolytic Streptococcus (GABHS).

• 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 (Figure 99-1), brown or dark crusts, erythematous erosions (Figure 99-3), ulcers in ecthyma (Figure 99-4), and bullae in bullous impetigo (Figures 99-5 to 99-7).