18th March 2024

Severe Cutaneous Adverse Reactions (SCARs)

SCARs comprise of several distinct conditions with overlapping features. They are all T cell-mediated:

• Acute Generalised Exanethematous Pustulosis (AGEP) – a rare pustular drug eruption characterised by superficial pustules which usually develop within two days of exposure to the culprit medication. The rash usually starts on the face or in axillary folds and may be associated with a fever, however patients very rarely deteriorate in contrast to other SCARs
• Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) – a severe multi-organ drug reaction including pyrexia, morbilliform skin eruption, eosinophilia and hepatic injury. Lymphadenopathy is often a feature. It is particularly associated with anticonvulsant medication. DRESS is slower to develop than AGEP and is usually seen within two to eight weeks of starting the responsible medication. Immediate withdrawal of the culprit drug is warranted and systemic immunosuppression is often required. Many patients require intensive care and this condition is associated with significant morbidity and mortality.
• Toxic Epidermal Necrolysis (TEN) – a very rare adverse drug reaction more commonly seen in drugs with longer washout periods. Timing of presentation can be variable but is usually within four weeks of drug exposure. TEN is more common in patients with Human Immunodeficiency Virus. Appearance of a painful, erythematous, diffuse rash is often preceded by pyrexia and flu-like illness. Mucosal involvement can be extremely severe with ocular, gastrointestinal, genital, urinary and respiratory tract pathology. Shock and multiple organ failure can develop rapidly.