The patient came with a history of bullae involving >30 % body surface area along with erosions of the lips and other mucosae for the past 7 days. What is the most probable underlying etiology?

Ans. c. Drugs (Ref: Neena Khanna 4/e p83) Image Courtesy- The above picture shows forearm with extensive reddish bullae involving >30% body surface area and description are typical of the spectrum of Steven-Johnson syndrome and toxic epidermal necrolysis. Toxic epidermal necrolysis (TEN), also known as Lyell's syndrome, is a rare, life-threatening skin condition that is usually caused by a reaction to drugs. Epidermal Necrolysis (EN) Also known as Stevens-Johnson syndrome-toxic epidermal necrolysis (SJS-TEN) complex. EN is almost always due to drugsQ. Etiology of Epidermal Necrolysis Drugs Miscellaneous Idiopathic * Anticonvulsants: carbamazepine, phenytoin barbiturates, lamotrigineQ * Chemotherapeutic agents: sulfonamides, penicillinQ * NSAIDs: Butazones, oxicams Others: Allopurinol nevirapineQ * SLE, GVHD * Lymphoreticular malignancies * Infections (Mycoplasma pneumoniae, herpes virus infection) * 5% of patients Morphology: Consists of deeply erythematous (often purpuric) irregular lesions that rapidly coalesce. Either develop bullae or peel-off in sheets either spontaneously or when pressure is applied (positive Nikolsky's signQ) On peeling, leave large areas of denuded skin that heal with hyperpigmentation. Based on total body surface area (BSA) of skin detached, EN classified into SJS <10% BSA SJS/TEN overlap (Stevens-Johnson syndrome- Toxic Epidermal Necrolysis) 10-30% BSA TEN > 30% BSAQ Sites: Symmetrical involvement of face, truck and proximal part of extremities; Spares distal part of extremities. Mucous membranes: Mouth and eyes frequently, other mucosae less frequently affected; manifest as hemorrhagic crusts and white pseudomembrane of the lips Complications: EN is an emergency, associated with high mortality due to: Infections: Including sepsis Fluid and electrolyte imbalance Pulmonary involvement: Interstitial syndrome Renal failure: A direct nephrotoxic effect of the drug or due to hypotension Ophthalmic complications: Acute complications and late sequelae like dry eyes, symblepharon Investigations: Biopsy: Subepidermal split with necrotic epidermisQ Provocation: Causative drug can be identified by provocation test, but this is controversial Treatment: General measures: Withdrawal of suspected drug with supportive care Specific therapy: Use of steroids is controversial. IVIg and cyclosporine are promising modalities.