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Author: Dr Helen Gordon, Dermatology Registrar, Greenlane Hospital, Auckland, New Zealand. DermNet New Zealand Editor in Chief: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy editor: Maria McGivern. April 2017.
A severe cutaneous adverse reaction (SCAR) to drugs include:
These are distinct conditions, but common features can be seen between the severe cutaneous adverse reactions creating diagnostic difficulty and there are cases where there is overlap of diagnostic criteria.
A multinational registry called the RegiSCAR Project has been formed to further examine severe cutaneous adverse reactions.
*Hydroxychloroquine resulted in widespread painful erosions, mucositis, flaccid vesicles, pustules. Biopsy was consistent with AGEP.
While the pathophysiology of severe cutaneous adverse reactions is not yet fully understood, the activation of drug-specific T lymphocytes has been implicated. Specific human leukocyte antigen alleles have been identified that are associated with an increased risk of forms of severe cutaneous adverse reaction.
AGEP features non-follicular sterile pustules.
DIHS/DRESS features rash, solid organ involvement (most commonly, the liver), fever, lymphadenopathy and facial oedema.
SJS/TEN often presents with a few days of prodromal illness with fever (> 39 C), malaise, cough, a blocked or runny nose, sore throat and sore eyes.
The severe cutaneous adverse reaction conditions are diagnosed from the patient history and a careful clinical examination; daignosis can be aided by investigations such as blood tests and skin biopsy.
Severe cutaneous adverse reactions will usually require hospital admission.
SJS/TEN, DIHS/DRESS and AGEP can share features, and there are also case reports of overlap where the full diagnostic criteria for more than one form of severe cutaneous adverse reaction have been met.
In a study of 117 patients with DIHS/DRESS using the RegiSCAR database, 30% had pustules, 16% blistering, and 56% had mild mucosal involvement.
A skin biopsy can help to distinguish between the severe cutaneous adverse reactions.
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