Toxic Epidermal Necrolysis

Description

• One of the most fulminant and potentially fatal of all mucocutaneous disorders
• Skin sloughing at the dermal–epidermal interface results in the equivalent of a second-degree burn
• Can affect up to 100% of total body surface area (BSA)
• May extend to involve:
  • GI mucosa
  • Respiratory mucosa
  • Genitourinary/renal epithelium
• Mechanism believed to be linked to T-cell–mediated cytotoxicity
  • A delayed type hypersensitivity reaction triggered by specific drugs, infections, or idiopathic triggers
  • Genetic susceptibility also appears to play a role
• Toxic epidermal necrolysis (TEN) is included in a disease continuum with Stevens–Johnson syndrome (SJS). Current classification system includes 3 categories based on percentage of total BSA:
  • SJS: <10% of BSA
  • SJS–TEN overlap syndrome: 10–30% of BSA
  • TEN: >30% of BSA, can affect up to 100% BSA
• Risk factors:
  • Age 1–10
  • Age >70
  • HIV
  • Active malignancy particularly hematologic
  • Liver and kidney disease
  • Genetic factors have been identified such as certain HLA types
• Mortality rate overall ranges from 10% for SJS to up to 34% for TEN, usually due to secondary sepsis, acute respiratory distress syndrome (ARDS), and multisystem organ failure
• Synonym(s):
  • Lyell syndrome
  • Epidermolysis necroticans combustiformis

• A recent study found lower mortality rates in children: 0% SJS, 4% SJS/TEN, and 16% TEN
• Predictors of mortality in children include: Renal failure, sepsis, epilepsy, any bacterial infection and malignancy

Etiology

• Dose-independent drug reactions are the usual cause of TEN:
  • Onset time varies, most commonly 4–28 d from initiation of medication, but may be delayed up to 30 wk
  • Frequently implicated drugs include:
    • Sulfonamide and PCN antibiotics
    • Anticonvulsants (carbamazepine, phenytoin, phenobarbital, lamotrigine)
    • NSAIDs (oxicams, pyrazoles, sulindac)
    • Allopurinol
    • Corticosteroids
    • Antiretroviral drugs
    • Herbal remedies
    • New biologic agents
• Other rare causes: Infections, specifically Mycoplasma pneumoniae in children, graft-versus-host disease, vaccinations, idiopathic cases (combined <4%)