The diagnosis of<unk>  may be forthright in typical cases in which an individual: has taken a drug known to cause the disorder; develops multiple sterile pustules overlying large areas of red swollen skin starting a few days after initial drug intake; and has a histology of biopsied lesions that shows pustules just below the skin's Stratum corneum (outermost layer), apoptotic (i.e. necrotic) keratinocytes, spongiosis of the stratum spinosum, and infiltration of these tissues by neutrophils plus, in many but not all cases, eosinophils. Many cases of<unk> , however, present less clear cut clinical features of the disorder.<unk>  must be differentiated from<unk>  pustular psoriasis (GPP) with which it shares many clinical and histological features. A history of psoriasis, the presence of typical psoriatic skin lesions at the time of diagnosis, and histological evidence in skin lesions of necrotic keratinocytes, neutrophil-rich infiltrates, eosinophil infiltrates, and/or lack of tortuous or dilated blood vessels favors a diagnosis of to<unk> . Other conditions sometimes confused with<unk>  include pustular eruptions caused by bacteria, funguses, herpesviridae, and the varicella zoster virus (i.e. causative agent of chicken pox). Several tests have been proposed to be useful for supporting the diagnosis of and/or implicating a particular drug as the cause of<unk>  particularly in individuals who develop skin lesions while taking multiple drugs. These include patch tests in which small amounts of suspect drugs absorbed on patches are applied to the skin; skin allergy tests in which drugs are applied by skin prick or intradermal injection; and oral provocation in which drugs are taken in a single small dose orally. These tests have not been widely adopted because of their insensitivity and, most particular with oral provocation tests, the possibility of causing a relapse or worsening or the disorder. In vitro tests, including mixed lymphocyte reaction tests in which the response of individuals' blood mononuclear cells to suspect drugs and ELISPOT tests in which specific drug-reactive lymphocytes or their drug-induced release of<unk>  mediators (e.g. interferon-γ interleukin 4, or granulysin) are measured have likewise not been broadly adopted because of their lack of specificity. Classification The disorder is classified in the group of severe cutaneous adverse reactions (i.e. SCARs). The SCARs group of disorders includes four other drug-induced skin reactions: drug reaction with eosinophilia and systemic symptoms (DRESS syndrome), Stevens–Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and Stevens–Johnson/toxic epidermal necrolysis overlap syndrome (SJS/TEN). SJS, SJS/TEN, and TEN, while initially described as distinct adverse drug-induced cutaneous reactions are now regarded as manifestations of epidermal necrolysis differing only in extent of skin involvement. While all of five SCARs disorders are potentially lethal,<unk>  has the lowest mortality of the group.
Acute generalized exanthematous pustulosis
Streptococcal intertrigo
Impetigo herpetiformis
Acute cutaneous lupus erythematosus
Polymorphous light eruption
Keratolytic winter erythema
Shingles
Herpetic whitlow