Anyone know about toxic epidermal necrolysis?!
Question:
Anyone know about toxic epidermal necrolysis?
need help to understand this
Answers:
Background: Described in 1956 by Alan Lyell, toxic epidermal necrolysis (TEN) is a rapidly evolving mucocutaneous reaction characterized by widespread erythema, necrosis, and bullous detachment of the epidermis resembling scalding.
TEN represents the most severe variant of a disease spectrum that consists of bullous erythema multiforme (EM) and Stevens-Johnson syndrome (SJS). Each of the disorders shares common features including widespread distribution of skin lesions, predominantly on the trunk and face with involvement of one or more mucus membranes.
A classification system based largely on the extent of epidermal detachment and morphology of the skin lesions helps in differentiating the disease entities.
* Bullous EM - Epidermal detachment less than 10% of body surface area involved with typical localized target lesions or “raised atypical targets”
* SJS - Epidermal detachment less than 10% of body surface area involved with widespread erythematous or purpuric macules or flat atypical targets
* Overlap SJS-TEN - Epidermal detachment between 10-30% of body surface area with widespread erythematous or purpuric macules or flat atypical targets
* TEN "with spots" - Epidermal detachment greater than 30% of the body surface area with widespread purpuric macules or flat atypical targets
* TEN "without spots" - Epidermal detachment greater than 30% of the body surface area in large epidermal sheets and without purpuric macules or targetlike lesions.
Histopathologic examination is necessary in differentiating these disorders from other severe bullous skin diseases such as staphylococcal scalded skin syndrome or paraneoplastic pemphigus. Initial ED management is therefore supportive.
Pathophysiology: Multiple pathophysiologic mechanisms have been proposed, although an immune-complex mediated phenomenon is likely responsible. One accepted theory suggests that accumulation of drug metabolites in the epidermis of genetically predisposed individuals induces an immunologic process analogous to that which occurs in graft-versus-host disease. CD8+ T lymphocytes and macrophages activate an inflammatory cascade, leading to widespread apoptosis of epidermal cells.
Frequency:
* Internationally: Worldwide, 0.4-1.2 cases per million population occur each year.
Mortality/Morbidity: TEN has a mortality rate of 30-40%. Epithelial loss results in vulnerability to bacterial and fungal infections and predisposes to septicemia, the leading cause of morbidity and mortality. Mucosal membranes are affected to a varying extent and can cause GI hemorrhage, respiratory failure, ocular abnormalities, and genitourinary lesions. Significant fluid loss from extensive skin lesions as well as an inability to tolerate oral intake can lead to hypovolemia, acute tubular necrosis, and shock.
* A severity-of-illness score that estimates the risk of death in TEN has been developed and validated (SCORTEN).
o Age >40 years
o Heart rate >120 beats per minute
o Cancer or hemopathy
o Involved body surface area >10%
o Blood urea nitrogen >10 mmol/L (10 mEq/L)
o Serum bicarbonate <20 mmol/L (20 mEq/L)
o Blood glucose 14 mmol/L (252 mg/dL)
* Mortality rates based upon the number of positive criteria are as follows:
o 0 to 1 factor = 3%
o 2 factors = 12%
o 3 factors = 35%
o 4 factors = 58%
o 5 or more factors = 90%
Age: SJS and TEN usually occur in adults but may be seen in children. Age older than 40 years is an independent risk factor for mortality.