Haemolytic uraemic syndrome

Haemolytic Uraemic Syndrome (HUS) is characterised by haemolytic anaemia, thrombocytopenia and acute renal failure in the absence of disseminated intravascular coagulation. Thrombosis in the microcirculation with consumptive thrombocytopenia and mechanical haemolytic anaemia with fragmented red cells results in ischaemic organ damage. The kidney is the organ predominantly affected but extra-renal manifestations may occur. Central nervous system involvement may cause seizures, altered consciousness, hemiparesis and brain stem dysfunction. Cardiomyopathy, liver dysfunction and diabetes are all recognised. Prodromal diarrhoea occurs in 90–95% of cases. This is referred to as typical or D + HUS. Young children are most commonly affected. Infection with shiga-like toxin producing E. coli is the most important risk factor. There is good evidence that the toxin plays a key role in pathogenesis. The 5% of cases in which there is no diarrhoeal prodrome are referred to as atypical HUS (aHUS). The mortality in the acute phase of D + HUS varies between 2 and 12% being higher in outbreaks. The mortality in the acute phase of aHUS is much higher at around 20%. Recent advances in understanding have led to the recognition of abnormalities of complement regulation, abnormal circulating von Willebrand factor multimers, infections and drugs as causes of atypical HUS.