Atypical haemolytic uraemic syndrome

Abstract

The haemolytic uraemic syndrome (HUS) is characterized by the triad of thrombocytopenia, microangiopathic haemolytic anaemia and acute renal failure. HUS may be classified as either diarrhoeal-associated or non-diarrhoeal/atypical (aHUS). aHUS has recently been shown to be a disease of complement dysregulation, with 50% of cases involving the complement regulatory genes, factor H (CFH), membrane cofactor protein (MCP; CD46), and factor I (IF). However, incomplete penetrance of mutations in each of these genes is reported. This suggests that a precipitating event or trigger is required to unmask the complement regulatory deficiency. The reported precipitating events predominantly cause endothelial injury. Discovery of these mutations has revealed important genotype-phenotype correlations. MCP-HUS has a better prognosis and a better outcome after transplantation than either CFH-HUS or IF-HUS.