🦠 Infectious Causes
• Herpes simplex (HSV): grouped vesicles on erythematous base, gingivostomatitis, herpes labialis
• Varicella (chickenpox): "dew drops on a rose petal," crops, centripetal distribution, all stages present
• Hand-foot-mouth disease (Coxsackievirus): oral ulcers, vesicles on palms/soles, buttocks
• Bullous impetigo: flaccid bullae, honey-crusted erosions (Staph aureus)
• Staphylococcal scalded skin syndrome (SSSS): Nikolsky sign, perioral crusting, superficial desquamation
⚠️ Serious Blistering Disorders (Emergencies)
• Stevens-Johnson syndrome (SJS): target lesions, ≥2 mucosal surfaces involvement (oral, ocular, genital)
• Toxic epidermal necrolysis (TEN): >30% BSA detachment, drug-induced
• Both: Nikolsky sign (skin slips with gentle pressure), medical emergency
🩺 Non-Infectious & Inherited
• Erythema multiforme (EM): target lesions (classic: three zones), symmetric, limited mucosal involvement (≤1 site). HSV-associated most common.
• Epidermolysis bullosa (EB): inherited blistering with trauma/friction, subtypes (simplex, junctional, dystrophic)
• Incontinentia pigmenti: X-linked dominant (females), vesicles → verrucous → hyperpigmented swirls, alopecia, dental/CNS/eye anomalies
• Linear IgA disease (chronic bullous dermatosis of childhood): "cluster of jewels" (sausage-shaped bullae in rosette)
📋 Other Causes
• Acrodermatitis enteropathica (zinc deficiency): perioral, acral, perineal vesicles/bullae, alopecia, diarrhea
• Dyshidrotic eczema (pompholyx): pruritic vesicles on palms/soles
• Miliaria (heat rash): tiny clear vesicles (miliaria crystallina) or erythematous papulovesicles (miliaria rubra)
• Sucking blisters: in utero, dorsal hands/forearms, benign
📌 Decision strategy: Nikolsky sign + toxic appearance + mucosal involvement → SJS/TEN (EMERGENCY). Target lesions without systemic toxicity → EM. Flaccid bullae with perioral crusting in infant → SSSS (Staph toxin).