LAUSR

Initial blood tests showed a creatinine concentration of 693 μmol/L (reference interval [RI], 63– 97 μmol/L), a platelet count of 46 × 109/L (RI, 150– 400 × 109/L) and a haemoglobin level of 104 g/L (RI, 115– 165 g/L). An urgent diagnostic workup was commenced to determine the cause of her renal failure, thrombocytopenia and anaemia (Box 1). A coagulopathy screen showed a fibrinogen level of 4.5 g/L (RI, 2– 4 g/L), a Ddimer level > 20 mg/L (RI, < 0.5 mg/L), and a normal international normalised ratio. This ruled out a coagulopathic cause but was suspicious for venous thromboembolism. Her haemolytic screen was consistent with haemolysis, showing a lactate dehydrogenase level of 2407 U/L (RI, 129– 250 U/L), a haptoglobin level < 0.1 g/L (range, 0.5– 2.2), a reticulocyte count of 71 × 109/L (RI, 10– 100 × 109/L), and a peripheral blood film with schistocytes and spherocytes (Box 2). Her direct antiglobulin test result was negative, ruling out immune haemolysis and confirming microangiopathic haemolytic anaemia (MAHA). Key differentials included thrombotic thrombocytopenic purpura (TTP), haemolytic uraemic syndrome (HUS) and complementmediated (atypical) HUS. She was admitted to the intensive care unit and treated provisionally for TTP with plasmapheresis, steroids and haemodialysis. Her ADAMTS13 level was 59% (RI, 60– 130%), ruling out TTP. Her stool sample was negative for Shiga toxin and she had normal complement C3/C4 levels.