Hemolytic Uremic Syndrome

Hemolytic uremic syndrome (HUS) is a life-threatening condition characterized by a triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. The most common form, typical HUS, is triggered by infection with Shiga toxin-producing Escherichia coli (STEC), particularly serotype O157:H7. This bacterium colonizes the intestinal mucosa and releases Shiga toxin (Stx), which enters the bloodstream and binds to globotriaosylceramide (Gb3) receptors concentrated on the surface of renal glomerular endothelial cells. Once internalized, Shiga toxin inhibits protein synthesis by cleaving ribosomal RNA, causing direct endothelial cell injury and death. The damaged endothelium triggers a cascade of thrombotic microangiopathy: platelets aggregate on the injured vascular surfaces forming microthrombi within small arterioles and capillaries, particularly in the renal glomeruli. These microthrombi partially occlude the vessel lumen, creating turbulent blood flow that mechanically shears red blood cells as they pass through the narrowed vessels, producing fragmented red blood cells called schistocytes. This mechanical destruction of red blood cells is the hallmark of microangiopathic hemolytic anemia. The platelet consumption in forming microthrombi leads to thrombocytopenia, while the occlusion of renal microvessels produces ischemic injury to...