Hemolytic uremic syndrome

Haemolytic uraemic syndrome (HUS) is a multisystem thrombotic microangiopathic disease characterised by the triad of renal failure, haemolytic anaemia and thrombocytopenia. It is the most common cause of renal failure in infancy and childhood requiring dialysis. 

There are two forms of this syndrome:

• typical or D+ HUS: corresponds to >90% of all HUS, occurs in childhood and is caused by Shiga toxin-producing Escherichia coli
• atypical or D- HUS: can occur after infections, use of certain drugs, following other pathologies (e.g. malignancy), or, rarely, due to defective cobalamin metabolism ³

This article is based on the features related to the typical HUS. 

Epidemiology

HUS affects ~ 2:100,000 people worldwide ³. 

Clinical presentation

It is most commonly seen in young children.

Usually, there is an interval of 2-12 days between the ingestion of contaminated food and the first day of diarrhoea and abdominal pain. After 1-3 days the diarrhoea becomes bloody (~90%). Fever is usually absent. 

Pathology

HUS usually occurs (>90%) following a gastrointestinal infection with Shiga toxin-producing E. coli (STEC). Some cases are associated with medical conditions such as collagen vascular conditions like SLE, underlying malignancy, or medications such as cyclosporine, OCP, or 5 FU. 

Injury to the endothelium of the capillaries results in mechanical destruction of the RBCs. Kidneys can be the only organ involved; however involvement of the other organ like liver, pancreas, heart, intestine, muscles also possible.

History and etymology

The term was coined by the Swiss doctor Conrad von Gasser in 1955. The relation of E. coli as an aetiological factor was proposed by Mohamed A. Karmali in 1985 ^2,4.