## Pathophysiology of SJS/TEN **Key Point:** SJS and TEN are severe cutaneous adverse reactions (SCAR) mediated by cytotoxic CD8+ T cells and natural killer cells, with granulysin playing a central role in keratinocyte apoptosis [cite:Robbins 10e Ch 25]. ## Mechanism of Keratinocyte Death The primary pathogenic mechanism involves: 1. Drug-specific CD8+ T cell infiltration into the epidermis 2. Granulysin release from cytotoxic lymphocytes 3. Massive keratinocyte apoptosis leading to full-thickness epidermal necrosis 4. Subepidermal blister formation due to loss of dermal-epidermal adhesion **Clinical Pearl:** Histology showing full-thickness epidermal necrosis with minimal dermal inflammation is pathognomonic for SJS/TEN and distinguishes it from other drug eruptions. ## Management Principles ### Immediate Interventions - **Discontinue the offending drug immediately** — this is non-negotiable - Avoid all structurally related drugs (e.g., other sulfonamides, NSAIDs, anticonvulsants) - Supportive care: IV fluids, electrolyte correction, temperature regulation, pain management - Ophthalmologic assessment for ocular involvement ### Immunomodulatory Therapy — The Controversy **High-Yield:** The role of systemic corticosteroids in SJS/TEN remains contentious: - **Early high-dose corticosteroids (≥2 mg/kg/day)** were traditionally avoided due to concerns about increased infection risk and poor wound healing - **Recent evidence** (2018 ASPC guidelines, RegiSCAR studies) suggests **early, high-dose corticosteroids may reduce mortality if given within 48 hours of onset**, particularly in SJS with <10% BSA involvement - However, **delayed initiation (>48 hours) or prolonged use is associated with worse outcomes** - **Alternative agents:** IVIG (2 g/kg over 3–5 days) and cyclosporine (3–5 mg/kg/day) are increasingly used, especially when corticosteroids are contraindicated **Warning:** The statement that "systemic corticosteroids in high doses reduce mortality" is **NOT universally accepted** as standard-of-care dogma in all guidelines. Many conservative dermatologists still advocate for supportive care alone, reserving immunomodulation for severe/progressive cases. This remains a high-yield exam trap. ### Supportive Care (Gold Standard) | Intervention | Rationale | |---|---| | Fluid and electrolyte management | Prevent hypovolemia and acute kidney injury | | Nutritional support | Maintain protein synthesis for wound healing | | Infection prevention | Sterile dressing, prophylactic antibiotics if indicated | | Pain control | Opioids, topical anesthetics | | Temperature regulation | Prevent sepsis-like complications | **Key Point:** Supportive care remains the cornerstone of SJS/TEN management regardless of immunomodulatory choice. ## Why This Distractor Is Correct The statement about high-dose corticosteroids reducing mortality is **the exception to the consensus**. While some recent studies support early corticosteroid use, this is NOT universally endorsed as standard-of-care in all major guidelines (e.g., UpToDate, many national dermatology societies still recommend caution). The traditional teaching — and what most NEET PG exams expect — is that **supportive care and drug withdrawal are primary**, with immunomodulation (IVIG/cyclosporine) reserved for severe cases, not routine high-dose corticosteroids. ## SJS vs TEN Classification | Feature | SJS | TEN | |---|---|---| | **BSA involvement** | <10% | >30% | | **Mucous membrane involvement** | Often | Nearly universal | | **Mortality** | 1–5% | 20–50% | | **Histology** | Full-thickness epidermal necrosis | Same | **Mnemonic:** **SJS-TEN Spectrum** = **S**evere **J**oints/**S**kin, **T**oxic **E**piderm **N**ecrosis — a continuum of the same disease.
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