A 55-year-old male was admitted to hospital and later to the ICU with refractory distributive shock thought to be sepsis of unknown origin. Two days after discharge the patient was readmitted to the ICU with a generalised skin eruption and multiple organ dysfunction syndrome. Extended microbiological testing and CT scans were negative for an infection. Azathioprine hypersensitivity syndrome, characterised by systemic symptoms such as fever, nausea, vomiting, diarrhoea, arthralgias, myalgias, liver and/or renal involvement and even shock, was thought to be the most likely diagnosis. Early recognition of this syndrome and the discontinuation of azathioprine seems vitally important to prevent morbidity or even mortality.