Toxic Epidermal Necrolysis (TEN)

A patient who develops fever, severe skin pain, dusky lesions, and rapidly forming flaccid bullae after starting a medication may be progressing toward toxic epidermal necrolysis (TEN), not experiencing a routine drug rash. The epidermis detaches and painful erosions often involve the mouth, eyes, and genital tract. This barrier failure produces burn-like fluid and heat loss, while mucosal injury can threaten vision, nutrition, the airway, and other organs. Classification depends on the amount of epidermis detached: Stevens–Johnson syndrome (SJS) involves <10% of body-surface area (BSA), SJS/TEN overlap involves 10–30%, and TEN involves >30%. The diagnosis is clinical and is supported by biopsy showing full-thickness epidermal necrosis. The first priority is to stop suspected culprit drugs started within the preceding 5–56 days, using the ALDEN approach to assess causality, and to arrange urgent ICU or specialized burn-centre care. In Canada, >10% BSA detached, a SCORTEN of ≥2, or any organ dysfunction warrants ICU or specialized burn-centre admission. The experienced clinician notices the combination of pain, mucosal involvement, rapid progression, and a plausible medication timeline. BSA measurement matters, but a seemingly limited...