Complement System As a Common Link in the Pathogenesis of Hemolytic Uremic Syndrome

Hemolytic uremic syndrome (HUS) is the most common cause of acute renal failure in children. The main causes of HUS are infections caused by Shiga toxin-producing bacteria: hemorrhagic Escherichia coli and Shigella dysenteriae type 1. They account for up to 90% of all cases of HUS. The remaining 10% represent a heterogeneous group of diseases collectively referred to as atypical HUS. The pathogenesis of most cases of atypical HUS is based on congenital or acquired disorders in the complement system. Over the past decades, evidence has accumulated that, in addition to E. coli and Sh. dysenteriae type 1, a wide variety of bacterial and viral infections, including the pathogens of pneumonia Streptococcus pneumoniae, immunodeficiency virus, H1N1 influenza, and a new coronavirus infection, can cause the development of HUS. In particular, infectious diseases act as the main cause of recurrence of atypical HUS. This review presents summarized data from recent studies, indicating that in various types of infectious HUS, disturbances in the complement system are a key pathogenetic factor. The links in the complement system are considered, the dysregulation of which in bacterial and viral infections can lead to complement hyperactivation with subsequent damage to the microvascular endothelium and the development of acute renal failure.