Glossary

Hemolytic Uremic Syndrome

Commonly abbreviated “HUS,” this is one of the two thrombotic microangiopathies, along with thrombotic thrombocytopenic purpura (TTP). Like TTP, HUS is associated with thrombocytopenia and changes of microangiopathic hemolytic anemia, but it is characterized by prominent acute renal failure. In contrast to TTP, most patients with HUS do not have abnormalities of the von Willebrand Factor cleaving enzyme ADAMTS13.

The vast majority of patients are children below age 5 who have a recent gastrointestinal infection (especially with E. coli O157:H17); this is so-called “typical” or “diarrhea-associated” HUS (D+HUS). 10% or so of patients with HUS, however, are adults who either have a disease or infection (including Streptococcus pneumoniae, HIV, cancer), are pregnant, are taking a mediation (including oral contraceptives and quinine), or have a defect in the inhibition of the complement system. All of the adult patients with HUS (no matter the cause) are grouped into the general category of “atypical HUS.” Treatment for D+HUS is simply supportive, but as many as half of the children affected must undergo dialysis. On the other hand, treatment for atypical HUS is controversial, with many if not most patients receiving therapeutic plasma exchange (TPE) despite the fact that it may not help in most cases.

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