Nonbullous impetigo is a highly contagious superficial skin infection. It is primarily caused by Staphylococcus aureus in industrialized countries. However, group A streptococcus (Streptococcus pyogenes) remains a common cause of nonbullous impetigo in developing countries. In temperate climates, S aureus causes 90%-95% of cases, and S pyogenes or a combination of both S aureus and S pyogenes account for 5%-10% of cases.

Nonbullous impetigo has a predilection for children, affecting around 12% of children, compared to affecting about 5% of adults globally. Minor trauma such as insect bites or abrasions can predispose to infection. Additional predisposing factors include a warm, humid climate, atopic dermatitis, and participation in contact sports.

Clinically, impetigo presents as erythematous vesicles and/or pustules that quickly transition into superficial erosions with a characteristic "honey-colored" crust. Lesions are most commonly seen on the face (eg, around the nose and mouth) and extremities. With the exception of mild lymphadenopathy, patients with impetigo generally have no associated systemic symptoms.

Approximately 50% of patients with nonbullous impetigo will experience recurrent episodes within 12 months and require repeated courses of antibiotics.

Although MRSA infection of the skin usually presents as recurrent furunculosis or skin abscesses, MRSA has been shown to cause impetigo in 1%-10% of cases. Culture and sensitivities should always be performed in patients with lesions suspicious for cutaneous infection, and empiric coverage for MRSA should be instituted if clinical suspicion is high.

Constitutional symptoms and fever are minimal.

An infrequent complication of impetigo is acute poststreptococcal glomerulonephritis (APSG), which is caused by particular serotypes of S pyogenes that are nephritogenic. APSG can occur in children as young as age 2 years, presenting with hypertension, dark urine, and edema. The risk of APSG is not reduced when antibiotic treatment is administered. Importantly, acute rheumatic fever has not been associated with impetigo.