A 6-year-old child presents with honey-crusted lesions on the face and exposed areas. Culture grows Staphylococcus aureus. Which feature best distinguishes non-bullous impetigo from bullous impetigo?

Explanation

## Distinguishing Non-Bullous from Bullous Impetigo ### Clinical Presentation Comparison | Feature | Non-Bullous Impetigo | Bullous Impetigo | |---------|---------------------|------------------| | **Lesion morphology** | Honey-colored crusts on erythematous base | Flaccid bullae → erosions | | **Preceding vesicles** | Absent; crusts form de novo | Present; blisters precede crusts | | **Causative organism** | S. aureus (most common) | S. aureus (exfoliative toxin-producing strains) | | **Exotoxin involvement** | No exotoxin; direct bacterial invasion | Exfoliative toxins (ETA, ETB) cause acantholysis | | **Frequency** | 70% of impetigo cases | 30% of impetigo cases | | **Crusts appearance** | Thick, adherent, honey/golden color | Thin, flaccid; erosions rather than crusts | ### Key Point: **The hallmark of non-bullous impetigo is the formation of honey-colored crusts WITHOUT preceding fluid-filled vesicles.** This occurs due to direct bacterial invasion of the epidermis, not exotoxin-mediated acantholysis. ### Clinical Pearl: **Bullous impetigo** is caused by exfoliative toxin-producing S. aureus strains (typically phage group II). These toxins cleave desmoglein-1 in the granular layer, creating intraepidermal acantholysis and flaccid bullae. Non-bullous impetigo lacks this exotoxin mechanism. ### High-Yield: Non-bullous impetigo accounts for ~70% of all impetigo cases in clinical practice. The **honey-crust without preceding vesicle** is the single best discriminating feature and is pathognomonic for this variant. ### Mnemonic: **HONEY = Non-bullous** (Honey-colored crusts, direct invasion, NO exotoxin) **BULLA = Bullous** (Blisters precede crusts, exotoxin-mediated acantholysis)