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.
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
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.)
Impetigo is the most superficial of bacterial skin infections. It causes honey crusts, bullae, and erosions.
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.
Widespread impetigo with honey-crusted erythematous lesions on the back of a 7-year-old child. (Reproduced with permission from Richard P. Usatine, MD.)
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.)