## Exotoxins in Staphylococcal Skin Infections **Key Point:** Exfoliative toxins (ETA and ETB) are serine proteases that cleave desmoglein-1 in the granular layer of the epidermis, causing intraepidermal acantholysis and blister formation characteristic of bullous impetigo. ### Mechanism of Bullae Formation Exfoliative toxins target **desmoglein-1** (a desmosomal adhesion protein), leading to: - Loss of cell-to-cell adhesion in the granular layer - Intraepidermal blister formation (subcorneal) - Flaccid bullae that rupture easily ### Other Staphylococcal Toxins and Their Roles | Toxin | Mechanism | Clinical Manifestation | |-------|-----------|------------------------| | **Exfoliative toxin (ETA/ETB)** | Serine protease; cleaves desmoglein-1 | Bullous impetigo, staphylococcal scalded skin syndrome (SSSS) | | **Alpha-hemolysin** | Pore-forming toxin; lyses RBCs and WBCs | Non-bullous impetigo, cellulitis | | **Panton-Valentine leukocidin (PVL)** | Bi-component toxin; kills neutrophils | Severe skin infections, abscesses, necrotizing pneumonia | | **TSST-1** | Superantigen; triggers massive T-cell activation | Toxic shock syndrome, scarlet fever-like rash | **High-Yield:** Bullous impetigo = exfoliative toxin; non-bullous impetigo = alpha-hemolysin and other proteases. **Clinical Pearl:** Bullous impetigo presents with large, flaccid bullae that rupture easily, leaving a thin, varnish-like crust. Non-bullous impetigo (more common, ~70% of cases) presents with honey-crusted lesions without preceding bullae. 
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