Editing Stevens–Johnson syndrome (section)

==Diagnosis==
The diagnosis is based on involvement of less than 10% of the skin.<ref name=GARD2015/> It is known as TEN when more than 30% of the skin is involved and an intermediate form with 10 to 30% involvement.<ref name=Orph2008/> A positive [[Nikolsky's sign]] is helpful in the diagnosis of SJS and TEN.<ref name=":0" /> A skin biopsy is helpful, but not required, to establish a diagnosis of SJS and TEN.<ref name=":0" />

=== Pathology ===
[[File:Confluent epidermal necrosis - very high mag.jpg|thumb|[[Micrograph]] showing full-thickness epidermal necrosis with a basket weave-like [[stratum corneum]] and separation of the [[dermis]] and [[Epidermis (skin)|epidermis]], skin [[biopsy]], [[H&E stain]]]]
SJS, like TEN and erythema multiforme, is characterized by confluent epidermal [[necrosis]] with minimal associated inflammation. The acuity is apparent from the (normal) basket weave-like pattern of the [[stratum corneum]].

=== Classification ===
Stevens–Johnson syndrome (SJS) is a milder form of [[toxic epidermal necrolysis]] (TEN).<ref>{{cite book |chapter-url= http://www.merckmanuals.com/professional/dermatologic_disorders/hypersensitivity_and_inflammatory_disorders/stevens-johnson_syndrome_sjs_and_toxic_epidermal_necrolysis_ten.html |chapter= Stevens–Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) |title= The Merck Manual |date= November 2013 |last= Rehmus |first= W. E. |edition= (online version) 19th |editor-last= Porter |editor-first= R. S. |location= Whitehouse Station, NJ |publisher= [[Merck & Co.]] |title-link= Merck Manual of Diagnosis and Therapy }}</ref> These conditions were first recognized in 1922.<ref name=pmid_20101062 /> A classification first published in 1993, that has been adopted as a consensus definition, identifies Stevens–Johnson syndrome, toxic epidermal necrolysis, and SJS/TEN overlap. All three are part of a spectrum of severe cutaneous reactions (SCAR) which affect skin and mucous membranes.<ref name="Mockenhaupt_2011" /> The distinction between SJS, SJS/TEN overlap, and TEN is based on the type of lesions and the amount of the body surface area with blisters and erosions.<ref name="Mockenhaupt_2011" /> It is agreed that the most reliable method to classify EM, SJS, and TEN is based on lesion morphology and extent of epidermal detachment.<ref name=":0" /> Blisters and erosions cover between 3% and 10% of the body in SJS, 11–30% in SJS/TEN overlap, and over 30% in TEN.<ref name="Mockenhaupt_2011" /> The skin pattern most commonly associated with SJS is widespread, often joined or touching (confluent), [[papule|papuric]] spots ([[macule]]s) or flat [[vesicle (dermatology)|small blisters]] or [[bulla (dermatology)|large blisters]] which may also join.<ref name="Mockenhaupt_2011" /> These occur primarily on the [[Trunk (anatomy)|torso]].<ref name="Mockenhaupt_2011" />

SJS, TEN, and SJS/TEN overlap can be mistaken for [[erythema multiforme]].<ref>{{cite journal | author = Auquier-Dunant A, Mockenhaupt M, Naldi L, Correia O, Schröder W, Roujeau JC | title = Correlations between clinical patterns and causes of Erythema Multiforme Majus, Stevens-Johnson Syndrome, and Toxic Epidermal Necrolysis results of an international prospective study | journal = [[JAMA Dermatology|Archives of Dermatology]] | volume = 138 | issue = 8 | pages = 1019–24 | date = 2002 | pmid = 12164739 | doi = 10.1001/archderm.138.8.1019 | last2 = Mockenhaupt | last3 = Naldi | last4 = Correia | last5 = Schröder | last6 = Roujeau | author7 = SCAR Study Group. Severe Cutaneous Adverse Reactions| doi-access =  }}</ref> Erythema multiforme, which is also within the SCAR spectrum, differs in clinical pattern and etiology.<ref name="Mockenhaupt_2011">{{cite journal | author = Mockenhaupt M | title = The current understanding of Stevens–Johnson syndrome and toxic epidermal necrolysis | journal = [[Expert Review of Clinical Immunology]] | volume = 7 | issue = 6 | pages = 803–15 | year = 2011 | pmid = 22014021 | doi = 10.1586/eci.11.66 | doi-access = free }}</ref>