Haemolytic uraemic syndrome: Case

This boy has typical STEC-associated haemolytic uraemic syndrome. The diagnosis rests on the triad of microangiopathic haemolytic anaemia (haemoglobin of 52 with schistocytes and helmet cells, elevated lactate dehydrogenase, undetectable haptoglobin, negative direct antiglobulin test), thrombocytopenia (platelets 36), and acute kidney injury (creatinine 230), following a bloody diarrhoeal prodrome eight days prior. The normal coagulation studies are critical because they confirm that this is HUS rather than disseminated intravascular coagulation, where the coagulation cascade would be systemically consumed. ^[1]

Clinical findings

The pattern is unequivocally that of STEC-HUS. The temporal sequence is classic: a five-day episode of bloody diarrhoea resolving three days before the onset of the haematological and renal features, placing the onset of HUS approximately eight days after the start of the prodrome, consistent with the typical 5 to 10 day interval. The haematological picture is that of intravascular haemolysis: schistocytes and helmet cells on the film reflect mechanical fragmentation of red blood cells in partially obstructed glomerular capillaries, the elevated lactate dehydrogenase reflects cell destruction, and the undetectable haptoglobin confirms that free haemoglobin is being released into the plasma. The negative direct antiglobulin test excludes autoimmune haemolysis and is essential for the diagnosis of a microangiopathic process. ^[1]

The thrombocytopenia is moderate (platelets 36) and reflects platelet consumption in the glomerular microthrombi, not a production problem. The acute kidney injury with elevated creatinine reflects the reduction in glomerular filtration surface area caused by the microvascular obstruction. The hypertension (blood pressure 118 over 78 in a 3-year-old, which is above the 95th centile for age) is driven by renin-mediated vasoconstriction from renal ischaemia and by volume overload from the oliguric renal failure. ^[1]