A 35-year-old man with a history of seizure disorder develops fever, conjunctivitis, and a widespread erythematous rash with blistering that began 14 days after starting phenytoin. Skin biopsy confirms toxic epidermal necrolysis (TEN) with >35% body surface area involvement. Regarding the clinical features, risk factors, and prognosis of SJS/TEN, all of the following statements are correct EXCEPT:

Explanation

## Risk Factors and Epidemiology of SJS/TEN **Key Point:** SJS/TEN is a rare but life-threatening drug reaction with an incidence of 1–2 per million person-years. The most common culprits vary by region and patient population [cite:Harrison 21e Ch 56]. ## High-Risk Drugs **High-Yield:** The most common offending agents are: | Drug Class | Frequency | Examples | |---|---|---| | **Anticonvulsants** | **30–40%** | Phenytoin, carbamazepine, phenobarbital, lamotrigine | | **NSAIDs** | 10–20% | Ibuprofen, naproxen, meloxicam | | **Antibiotics** | 15–25% | Trimethoprim-sulfamethoxazole, penicillins, fluoroquinolones | | **Allopurinol** | 5–10% | Especially in renal impairment | | **Antiretrovirals** | 5–10% | Nevirapine, abacavir | **Warning:** The statement that anticonvulsants account for **<5%** of cases is **FALSE**. Anticonvulsants (particularly phenytoin and carbamazepine) are among the **most common culprits**, accounting for **30–40%** of SJS/TEN cases, especially in patients with seizure disorders. ## Mortality Risk Factors **Mnemonic:** **SCORTEN** = **S**ex (female), **C**arcinoma (malignancy), **O**lder age (>40), **R**ate of progression (BSA >10% in first 24 hrs), **T**EN (vs SJS), **E**lectrolytes (urea >28 mg/dL), **N**eutrophils (<1500/μL) ### SCORTEN Scoring System | Parameter | Points | |---|---| | Age >40 years | 1 | | Heart rate >120 bpm | 1 | | Serum urea >10 mmol/L (>28 mg/dL) | 1 | | Serum glucose >14 mmol/L (>252 mg/dL) | 1 | | Active malignancy | 1 | | Percentage of BSA detached on day 1 | 1 (if >10%) | | Percentage of BSA detached on day 3 | 1 (if >50%) | **Key Point:** SCORTEN score ≥3 predicts **>35% mortality**; score 0–1 predicts <3.5% mortality. **Clinical Pearl:** Female gender is associated with higher mortality in SJS/TEN, likely due to delayed diagnosis and more severe systemic involvement. ## Ocular Involvement **High-Yield:** Ocular complications occur in **50–80%** of SJS/TEN cases and include: - Conjunctivitis and keratitis - Symblepharon (adhesion of conjunctiva to eyelid) - Corneal ulceration and scarring - Permanent blindness if untreated **Clinical Pearl:** Early ophthalmologic assessment and aggressive topical management (preservative-free lubricants, topical corticosteroids, cycloplegics) are essential to prevent long-term sequelae. ## Why This Distractor Is Correct The statement that anticonvulsants account for **<5%** of SJS/TEN cases is **factually incorrect**. In reality, anticonvulsants (especially phenytoin, carbamazepine, and phenobarbital) are among the **top culprits**, accounting for **30–40%** of all SJS/TEN cases. This is a high-yield exam point because phenytoin is one of the classic "must-know" triggers of SJS/TEN. ## SJS/TEN Prognosis and Complications | Complication | Frequency | Management | |---|---|---| | **Ocular** | 50–80% | Ophthalmology referral, topical care | | **Pulmonary** | 10–15% | Monitor for ARDS, mechanical ventilation if needed | | **Renal** | 5–10% | Fluid management, avoid nephrotoxic drugs | | **Infection** | 20–30% | Prophylactic antibiotics, sterile dressing | | **Contractures** | 15–25% | Early physical therapy, splinting | **Warning:** Mortality in TEN (>30% BSA) is 20–50%, making it a true dermatologic emergency.