Allopurinol-Induced Toxic Epidermal Necrolysis Following A Sub-Minimal Starting Dose: A Multidisciplinary Management Challenge

Toxic Epidermal Necrolysis (TEN) is a rare, severe mucocutaneous drug reaction within a single clinical spectrum, distinguished by epidermal detachment involving>30% of body surface area (BSA). Allopurinol is among the most common causative agents, particularly in patients newly started on therapy, and carries a well-established pharmacogenomic association with the HLA-B*58:01 allele. We present the case of a 55-year-old woman with newly diagnosed hyperuricemia who developed generalized pruritus within hours of taking half of a 300-mg allopurinol tablet, followed by burning in the bilateral axillary and inguinal regions and erythema of the trunk and abdomen. Within hours, she developed flaccid bullae with a positive Nikolsky sign, together with periorbital, conjunctival, oral, and vulvovaginal mucosal involvement. She was admitted to the intensive care unit with a diagnosis of Stevens-Johnson syndrome, an initial epidermal detachment under 10% of body surface area, and a SCORTEN of 1 (predicted mortality 3.2%). Gynecology was consulted for vulvovaginal ulceration and atrophic mucosa. Cutaneous detachment progressed to involve approximately 40-50% of BSA, requiring three staged surgical washouts and debridements with application of a porcine-derived extracellular matrix wound dressing to promote re-epithelialization. The hospital course was further complicated by transient vasopressor-requiring hypotension, chronic hypo-osmolar hyponatremia, probable relative adrenal insufficiency following corticosteroid tapering, opioid-associated ileus, and recurrent hypoglycemia, all managed supportively without evidence of superimposed infection. After 15 days in the intensive care unit, the patient was transferred to the internal medicine ward with favorable re-epithelialization of cutaneous lesions and resolution of cervicovaginitis. This case illustrates the fast development and multisystem nature of allopurinol-induced SJS/TEN overlap and the value of early, protocolized multidisciplinary management.