Impetigo & Ecthyma

Definition

Impetigo is a superficial bacterial skin infection, primarily caused by Staphylococcus aureus or Streptococcus pyogenes, characterized by pustules and honey-colored crusts. Ecthyma is a deeper ulcerative form of impetigo extending into the dermis.

Epidemiology

• Common in children, particularly 2–5 years old, but can affect adults
• More prevalent in warm, humid climates and crowded living conditions
• Outbreaks can occur in schools or daycare settings
• Higher incidence in children with eczema or other skin barrier defects
• Ecthyma is less common but more severe, often in malnourished or immunocompromised patients

Etiology

• Caused by Staphylococcus aureus (most common) and/or Streptococcus pyogenes
• Transmission: direct contact with infected lesions, fomites, or via scratching
• Risk factors: poor hygiene, minor skin trauma, insect bites, underlying skin conditions
• Ecthyma often occurs following untreated or severe impetigo

Pathophysiology

• Bacteria colonize the superficial epidermis, producing toxins and enzymes that cause vesicle and pustule formation
• Streptococcal infection triggers local inflammation and immune response
• Ecthyma involves deeper dermis, leading to ulceration with a necrotic base and crust formation
• Lesions can serve as a portal of entry for secondary bacterial infection
• Healing usually occurs without scarring in impetigo; ecthyma may leave mild scarring