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Diagnosis

Clinical diagnosis

Early recognition is the first step to treating toxic epidermal necrolysis (TEN). In at least half of the patients, TEN starts with one to two weeks of symptoms including fever, malaise, headache, cough, sore throat and diarrhea (1). This is often followed by lesions of the mucous membrane mainly in the oral cavity and the lips (1). Oral lesions are painful and may cause eating and breathing problems in patients (1). As for cutaneous involvement, macular rash initially appears on the face, neck, chin and trunk, then may spread to the extremities (1). Lesions have a similar appearance to target lesions, or have an irregular round shape with pale livid macules. Lesions are flat, tender and larger than target lesions (2,9). These lesions continue to spread for four to five days and often coalesce forming areas of loose and detachable epidermis (1). Large flaccid blisters also appear in TEN patients, resulting in necrotic epidermal sheets sloughing off. In rare situations, severe internal organ involvement can occur in TEN including respiratory and gastrointestinal organs (1).

Lymphocyte toxicity assay

Lymphocyte toxicity assay is a novel approach to assess drug hypersensitivity syndrome (10). Lymphocytes represent a suitable target for analysis because of accessibility, lack of enzymes that produce toxic metabolites of the parent drug, possess the enzymes necessary for detoxification and phenotypically express any genetic deficiencies in detoxifying enzymes (10). Experiments by Neumann and colleagues determined that lymphocyte toxicity assay was a useful ancillary diagnostic tool to determine drug hypersensitivity syndrome (10).