Hemolytic uremic syndrome

Hemolytic-uremic syndrome
as seen in a person with hemolytic-uremic syndrome
Classification and external resources
Specialty	Nephrology
ICD-10	D59.3
ICD-9-CM	283.11
OMIM	235400
DiseasesDB	13052
MedlinePlus	000510
eMedicine	ped/960
MeSH	D006463
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Hemolytic-uremic syndrome (or haemolytic-uraemic syndrome), abbreviated HUS, is a disease characterized by hemolytic anemia (anemia caused by destruction of red blood cells), acute kidney failure (uremia), and a low platelet count (thrombocytopenia). It predominantly, but not exclusively, affects children. Most cases are preceded by an episode of infectious, sometimes bloody, diarrhea acquired as a foodborne illness or from a contaminated water supply caused by E. coli O157:H7, other non-o157:H7 E. coli serotypes, Shigella, and Campylobacter. A variety of viruses have also been implicated as a causative agent. It is now the most common cause of acquired acute renal failure in childhood. It is a medical emergency and carries a 5–10% mortality rate; of the remainder, the majority recover without major consequences, approximately 30% suffer residual renal injury. The primary target appears to be the vascular endothelial cell. This may explain the pathogenesis of HUS, in which a characteristic renal lesion is capillary microangiopathy.

HUS was first defined as a syndrome in 1955. The more common form of the disease, Shiga-like toxin-producing E. coli HUS (STEC-HUS), is triggered by the infectious agent E. coli O157:H7, and several other non-O157:H7 E. coli serotypes. Certain Shiga toxin-secreting strains of Shigella dysenteriae can also cause HUS. Approximately 5% of cases are classified as pneumococcal HUS, which results from infection by Streptococcus pneumoniae, the agent that causes traditional lobar pneumonia. There is also a rare, chronic, and severe form known as atypical hemolytic uremic syndrome (aHUS), which is caused by genetic defects resulting in chronic, uncontrolled complement activation. Both STEC-HUS and aHUS cause endothelial damage, leukocyte activation, platelet activation, and widespread inflammation and multiple thromboses in the small blood vessels, a condition known as systemic thrombotic microangiopathy (TMA), which leads to thrombotic events as well as organ damage/failure and death.

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