Uncommon adult causes
Clinical Clues
- Waxy palmoplantar keratoderma (early sign)
- Salmon-orange-red color
- Large scales
- Follicular keratotic papules on knees, elbows, dorsal fingers
- Islands of sparing
Histologic clues
- Psoriasiform epidermal hyperplasia
- Normal granular layer
- Alternating para/orthokeratosis vertically and horizontally
- Follicular plugs with “shoulder parakeratosis”
- Absence of neutrophils
Other clues
- Flares post sun exposure
- Cephalocaudal progression
- Erythema gyratum-like lesions as condition resolves
Clinical Clues
- Fine scales
- Melanoerythroderma
- Cachexia
Histologic clues
Other clues
- Secondary to lymphoproliferative disorders > thymomas
- Solid organ malignancies (late stage)
Clinical Clues
- Pre-existing lesions
- Impetigo-like erosions/vesicles
- Crusted scale
Histologic clues
- Superficial epidermal acantholysis
- Direct immunofluorescence: intercellular IgG
Other clues
- Most common immunobullous disorder causing erythroderma
- Indirect immunofluorescence: intercellular
Clinical Clues
- Urticarial plaques
- Tense bullae
- Elderly patients
Histologic clues
- Subepidermal blister
- Eosinophils
- Direct immunofluorescence: basement membrane zone C3 and IgG
Other clues
- Indirect immunofluorescence: basement membrane zone
Clinical Clues
- Mucosal erosions
- Hemorrhagic crusts
- Mucocutaneous lichenoid lesions
- Erythema multiforme-like lesions
Histologic clues
- Interface dermatitis with necrotic keratinocytes
- Parakeratosis
- Focal acantholysis
- Direct immunofluorescence: intercellular and basement membrane zone IgG
Other clues
- Indirect immunofluorescence: intercellular and basement membrane zone (+ indirect immunofluorescence rat bladder)
