Cellulitis & Erysipelas (Pediatric)

Definition

Cellulitis and erysipelas are acute bacterial skin infections in children, involving the deeper dermis and subcutaneous tissue (cellulitis) or the upper dermis with well-demarcated borders (erysipelas), commonly caused by Streptococcus or Staphylococcus species.

Epidemiology

• More common in children under 5 years
• Seasonal peaks in warmer, humid months
• Risk factors: skin trauma, insect bites, eczema, immunodeficiency
• Bacterial etiology varies by region; group A Streptococcus is most common in erysipelas, Staphylococcus aureus in cellulitis
• Recurrence is common in children with predisposing conditions

Etiology

• Bacterial infection: Streptococcus pyogenes (group A), Staphylococcus aureus (including MRSA), less commonly Streptococcus agalactiae
• Skin barrier disruption: cuts, abrasions, insect bites, surgical wounds
• Underlying conditions: atopic dermatitis, fungal infections, edema
• Immune deficiency increases susceptibility
• Transmission via direct inoculation of bacteria into skin

Pathophysiology

• Bacterial invasion through skin breaches triggers inflammatory response
• Release of cytokines and chemokines leads to erythema, warmth, and edema
• Neutrophil infiltration and vascular permeability contribute to swelling and tenderness
• Toxin production in some strains causes systemic symptoms
• Erysipelas involves superficial dermis with sharply demarcated borders
• Cellulitis involves deeper dermis and subcutaneous tissue, often with diffuse margins