Outline the diagnostic features of Toxic Epidermal Necrolysis and list the likely causes in patients in Intensive Care.
TEN is condition involving rapid progression of erythems and extensive (usually > 30% epidermis involved) epidermal necrolysis. It overlaps with the Stevens-Johnson syndrome, and has a high mortality rate (up to 44%!). Early dermatological consultation is important. Diagnostic features include:
• Skin eruption that begins 1-3 weeks after starting a suspicious drug
• A prodrome of fever and flu-like symptoms, 1-3 days before eruption
Poorly defined macules with purpuric centres that coalesce to form blisters, and then epidermal detachment (involving > 30% epidermis)
• Symmetrical, primarily over face and upper trunk
• Burning or painful lesions (with complications similar to extensive thermal burns)
• Mucosal involvement in 90% (eg. conjunctiva, mouth, oesophagus, genital)
• Pulmonary complications can occur (eg. excessive-secretions, sloughing of bronchial epithelium, BOOP)
Most cases are drug induced, few are idiosyncratic. The commenest drugs to be implicated are: sulphonamides antibiotics, aminopenicillins, quinolones, cephalosporins, carbemazepine, phenobarbital, phenytoin, valproic acid, NSAIDs, allopurinol and corticosteroids! TEN is more common in patients with SLE and HIV.
Stevens-Johnson Syndrome and TEN are considered diseases of the same spectrum. SJS is the less severe classification of the same disease: only ~ 10% of the skin surface is sloughed. TEN, on the other hand, is a condition of over 30% slough. In the 10-30% patients, the two conditions overlap. This condition had come up again thirteen years later, in Question 28 from the second paper of 2018 which asked for a lot more detail about TEN, and which was actually done much better (pass rate was 58.2%).
Thus, the diagnostic features:
- History of exposure to a new drug
- 1-3 weeks of waiting
- Fever and flu-like symptoms for 1-3 days before skin eruption
- Skin eruption: poorly defined macules with purpuric centres
- Then, blisters and epidermal detachment
- Symmetrical, primarily over face and upper trunk
- Complications similar to burns
- Mucosal involvement in 90%
- BOOP and respiratory mucosal sloughing can also occur
Drugs which are known to cause TEN:
Non-drug causes of TEN:
- Mycoplasma pneumoniae (next most common cause)
- Influenza virus
- Malignancy (though this is usually listed as a risk factor or association)
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