A retrospective review was performed on cases of DRESS managed in our institution from 2005 through 2011. All patients were recruited onto the SCAR-UK registry (Severe Cutaneous Adverse Reactions, United Kingdom). All cases were defined as probable or definite DRESS based on the RegiSCAR diagnostic criteria.6 Patients were either admitted following presentation or were already inpatients at the time of diagnosis. Case records were systematically reviewed, and data on initial clinical presentation, laboratory parameters, initial diagnosis, and treatment were collected. Diagnostic lag was defined as the interval from initial diagnosis at presentation to time of DRESS diagnosis. This study was approved by our institutional review board at King's College Hospital, London, England.