Insights into pregnancy associated and atypical hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is defined by microangiopathic hemolytic anemia, renal dysfunction, and thrombocytopenia.1 It is the result of an insult to endothelial cells that may be caused by different mechanisms including Shiga toxin-induced HUS, autoimmune diseases, drugs, infections, and pregnancy (p-HUS).2 Atypical HUS (aHUS), unlike HUS, is associated with genetic or acquired dysfunction of the alternative complement pathway.3 Pregnancy and postpartum are recognized as specific triggers of aHUS, and this association led to the now recognized entity of pregnancy-associated aHUS (p-aHUS).4 p-aHUS is a rare and life-threatening disease that affects approximately 1 in 25,000 pregnancies.5 There is no specific test and the diagnosis of this syndrome may be challenging, as the clinical characteristics are very similar to severe preeclampsia and hemolysis elevated liver enzymes and low platelet syndrome (HELLP). In the past, plasmapheresis and fresh frozen plasma (FFP) were the two most reported treatments. However, more recently, eculizumab, a humanized monocolonal antibody to complement component five (C5), has been used.6 In 2017, three cohort studies were published which we review below (Table 1). They provide valuable data to understand the presentation, outcomes and other specific characteristics of p-aHUS