Atypical hemolytic uremic syndrome.

Hemolytic uremic syndromes are a heterogeneous group of conditions with differing underlying pathophysiology. These all result in pathologic features of thrombotic microangiopathy (TMA), which cause endothelial damage and organ injury. TMAs manifest with a microangiopathic hemolytic anaemia, thrombocytopenia, and commonly acute kidney injury. The past two decades have revealed many of the immunologic, metabolic, ribosomal, cell-signaling, and clotting pathways responsible for disease. The understanding of the role of the membrane attack complex in some TMAs has led to the introduction of pharmacologic inhibition of complement C5, which greatly improved prognosis. This review summarizes the current understanding of the pathogenesis of complement-dependent and non-complement-dependent TMAs.