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| __NOTOC__
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| {{CMG}}
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| {{Drug allergy}}
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| ==Overview==
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| '''Toxic Epidermal Necrolysis''' (TEN), also known as '''Lyell's syndrome''', is a life-threatening [[dermatology|dermatological]] condition that is frequently induced by a reaction to medications.<ref name=garra/> It is characterized by the detachment of the top layer of skin (the [[epidermis]]) from the lower layers of the skin (the [[dermis]]) all over the body. There is broad agreement in the medical literature that TEN can be considered a more severe form of [[Stevens-Johnson syndrome]] and debate whether it falls on a spectrum of disease that includes [[erythema multiforme]].<ref>{{cite journal |author=Carrozzo M, Togliatto M, Gandolfo S |title=[Erythema multiforme. A heterogeneous pathologic phenotype] |journal=Minerva Stomatol |volume=48 |issue=5 |pages=217-26 |year=1999 |pmid=10434539}}</ref><ref>{{cite journal |author=Farthing P, Bagan J, Scully C |title=Mucosal disease series. Number IV. Erythema multiforme |journal=Oral Dis |volume=11 |issue=5 |pages=261-7 |year=2005 |pmid=16120111}}</ref> The [[incidence (epidemiology)|incidence]] is between 0.4 and 1.2 cases per million each year.<ref name=garra/>
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| ==Pathogenesis==
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| Microscopically, TEN causes [[cell death]] throughout the epidermis. [[Keratinocytes]], which are the cells found lower in the dermis, specialize in holding the skin cells together, undergo [[necrosis]] (uncontrolled cell death).
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| ==Etiology==
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| Toxic epidermal necrolysis is a rare and usually severe adverse reaction to certain drugs. History of medication use exists in over 95% of patients with TEN.<ref name=garra/> The drugs most often implicated in TEN are antibiotics such as sulfonamides; [[nonsteroidal anti-inflammatory drugs]]; [[allopurinol]], [[antiretroviral drugs]]; and [[corticosteroids]]; and [[anticonvulsant]]s such as [[phenobarbital]], [[phenytoin]], [[carbamazepine]], and [[valproic acid]].<ref name=garra/> The condition might also result from immunizations, infection with agents such as ''[[Mycoplasma pneumoniae]]'' or the [[herpes virus]]; and [[Organ transplant|transplant]]s of [[bone marrow]] or organs.<ref name=garra/>
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| ==Symptoms==
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| TEN affects many parts of the body, but it most severely affects the [[mucous membrane]]s, such as the [[mouth]], [[eyes]], and [[vagina]]. The severe findings of TEN are often preceded by 1 to 2 weeks of [[fever]]. These symptoms may mimic those of a common [[upper respiratory tract infection]]. When the [[rash]] appears it may be over large and varied parts of the body, and it is usually warm and appears red. In hours, the skin becomes painful and the epidermis can be easily peeled away from the underlying dermis. The mouth becomes blistered and eroded, making eating difficult and sometimes necessitating feeding through a [[nasogastric tube]] through the nose or a gastric tube directly into the stomach. The eyes are affected, becoming swollen, crusted, and ulcerated.
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| ==Diagnosis==
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| Often, the diagnosis can be made clinically. Generally, if the clinical history is consistent with Stevens-Johnson syndrome, and the skin lesion covers greater than 30% of the body surface area, the diagnosis of TEN is appropriate. Sometimes, however, examination of affected tissue under the microscope may be needed to distinguish it between other entities such as [[staphylococcal scalded skin syndrome]]. Typical histological criteria of TEN include mild infiltrate of lymphocytes which may obscure the dermoepidermal junction and prominent cell death with basal vacuolar change and individual cell necrosis.<ref>{{cite journal |author=Pereira FA, Mudgil AV, Rosmarin DM |title=Toxic Epidermal Necrolysis |journal=J Am Acad Dermatol |volume=56 |issue=2 |pages=181-200 |year=2007 |pmid=17224365}}</ref>
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| ==Treatment==
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| First Line: early withdrawal of culprit drugs, early referral and management in burn units or [[intensive care unit]]s, supportive management, nutritional support
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| Second Line: [[Intravenous immunoglobulin]] (IVIG) - Uncontrolled trials showed promising effect of IVIG on treatment of TEN; a [[randomized control trial]] is needed in the future to determine the efficacy of IVIG in TEN.
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| Third Line: [[cyclosporin]], [[cyclophosphamide]], [[plasmapheresis]], [[pentoxifylline]], [[N-acetylcysteine]], [[ulinastatin]], [[infliximab]], Granulocyte colony-stimulating factors (if TEN associated-leukopenia)
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| Systemic steroids are unlikely to offer any benefits.
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| ==Prognosis==
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| The mortality for toxic epidermal necrolysis is 30-40 per cent.<ref name=garra>Garra, GP (2007). "[http://www.emedicine.com/EMERG/topic599.htm Toxic Epidermal Necrolysis]". Emedicine.com. Retrieved on December 13, 2007.</ref> Loss of the skin leaves patients vulnerable to infections from fungi and bacteria, and can result in [[septicemia]], the leading cause of death in the disease.<ref name=garra/> Death is caused either by [[infection]] or by [[respiratory distress]] which is either due to [[pneumonia]] or damage to the linings of the airway. Microscopic analysis of tissue (especially the degree of dermal mononuclear inflammation and the degree of inflammation in general) can play a role in determining the prognosis of individual cases.<ref>{{cite journal |author=Quinn AM et al |title=Uncovering histological criteria with prognostic significance in toxic epidermal necrolysis |journal=Arch Dermatol |volume=141 |issue=6 |pages=683-7 |year=2005 |pmid=15967913}}</ref>
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| ==References==
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| {{Reflist|2}}
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| ==See also==
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| * [[Stevens-Johnson syndrome]]
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| ==External links==
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| * {{MerckHome|18|203|e}}
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| * [http://www.sjsupport.org Stevens Johnson Syndrome Foundation]
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| * [http://www.avimedi.net/stevens-johnson-syndrome-home.html Association of victims of medicines]
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| * [http://www.dermnetnz.org/reactions/toxic-epidermal-necrolysis.html DermNetNZ]
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