What's new in haemolytic uraemic syndrome?

Recent advances in understanding the aetiology of the disorders that make up the haemolytic uraemic syndrome (HUS) permit a revised classification of the syndrome. With appropriate laboratory support, an aetiologically-based subgroup diagnosis can be made in all but a few cases. HUS caused by enterohaemorrhagic Escherichia coli remains by far the most prevalent subgroup, and new insights into this zoonosis are discussed. The most rapidly expanding area of interest is the subgroup of inherited and acquired abnormalities of complement regulation. Details of the pathogenesis are incomplete but it is reasonable to conclude that local activation of the alternative pathway of complement in the glomerulus is a central event. There is no evidence-based treatment for this diagnostic subgroup. However, in circumstances where there is a mutated plasma factor such as complement factor H, strategies to replace the abnormal protein by plasmapheresis or more radically by liver transplantation are logical, and anecdotal successes are reported. In summary, the clinical presentation of HUS gives a strong indication as to the underlying cause. Patients without evidence of EHEC infection should be fully investigated to determine the aetiology. Where complement abnormalities are suspected there is a strong argument for empirical and early plasma exchange, although rapid advances in this field may provide more specific treatments in the near future.