Learning Objectives
Differentiate between reactive and inherited blistering disorders. Master the association between Dermatitis Herpetiformis and Celiac disease, identify the Target Lesion as the hallmark of Erythema Multiforme, and distinguish the severity and progression of SJS vs. TEN.
1. Reactive & Autoimmune Blistering
These disorders are typically triggered by systemic disease, infections, or specific immune deposits within the skin layers.
| Condition | Pathophysiology / Triggers | Key Clinical Features |
|---|---|---|
| Dermatitis Herpetiformis | IgA deposits at the tips of dermal papillae. Strongly associated with Celiac disease. | Intensely pruritic vesicles on elbows, knees, and buttocks. Treat with Dapsone and gluten-free diet. |
| Erythema Multiforme (EM) | Hypersensitivity to HSV, Mycoplasma, or drugs (Sulfa, Phenytoin). | Target lesions (multiple rings with a dusky center). Multiple lesion types (macules, papules). |
2. Severe Cutaneous Adverse Reactions (SCAR)
These represent a medical emergency characterized by extensive skin sloughing at the dermal-epidermal junction, usually secondary to drug reactions.
| Condition | Body Surface Area (BSA) | Clinical Features |
|---|---|---|
| Stevens-Johnson (SJS) | < 10% skin involvement. | Fever, bullae, (+) Nikolsky sign, and mucous membrane involvement. |
| SJS-TEN Overlap | 10% – 30% involvement. | Progressive necrosis and sloughing. |
| Toxic Epidermal Necrolysis (TEN) | > 30% skin involvement. | Highest mortality rate; severe systemic toxicity. |
3. Inherited Mechanical Blistering
Genetic mutations in structural proteins lead to skin fragility, where even minor friction causes significant damage.
| Condition | Genetic Defect | Clinical Presentation |
|---|---|---|
| Epidermolysis Bullosa | Mutations in Keratin genes (e.g., K5/K14). | Blisters triggered by minor trauma; oral blisters noted during infant bottle feeding. |
Activity
High-Yield Mnemonics & Tips:
- Dermatitis Herpetiformis: Dermatitis Herpetiformis = Dapsone + Has Celiac disease.
- SJS/TEN: If the prompt mentions Nikolsky (+) and a New Drug (Allopurinol, Sulfa, Anticonvulsants), check the BSA percentage to choose between SJS and TEN.
- Target Lesions: Not all targets are SJS; Erythema Multiforme is the “classic” target-maker, often following an HSV (Cold sore) outbreak.