[Hemolytic uremic syndrome in adults]

Area of Science:

• Nephrology
• Hematology
• Immunology

Context:

• Hemolytic uremic syndrome (HUS) is a severe condition characterized by renal thrombotic microangiopathy, hypertension, and acute renal failure (ARF).
• Pathogenesis involves microvascular endothelial cell injury, often triggered by bacterial toxins, drugs, or autoantibodies, and can involve dysregulation of the complement alternative pathway.
• Deficiencies in regulatory proteins (factor H, I, MCP) or mutations in complement components (factor B, C3) predispose individuals to HUS, as does deficiency in ADAMTS-13, a von Willebrand factor cleaving protease.

Purpose:

• To provide a comprehensive overview of the pathogenesis, clinical manifestations, and therapeutic strategies for Hemolytic Uremic Syndrome (HUS).
• To highlight the diverse etiologies of HUS, including infectious, genetic, drug-induced, and autoimmune factors.
• To discuss the diagnostic criteria, prognostic factors, and evolving treatment landscape for HUS.

Summary:

• HUS presents with hemolytic anemia (schistocytes), thrombocytopenia, and renal failure. Typical HUS often follows infectious diarrhea (e.g., E. coli O157:H7), while atypical HUS lacks diarrhea and may involve complement dysregulation or thrombomodulin mutations.
• Specific triggers include postpartum states, certain chemotherapies (mitomycin C, gemcitabine), immunosuppressants (cyclosporine A, tacrolimus), and anti-VEGF antibodies (bevacizumab). HUS can also be associated with underlying chronic nephropathies in adults.
• Management strategies include plasma infusions/exchanges for hemolysis and thrombocytopenia. Steroids and immunosuppressants are debated; novel therapies like anti-C5 antibodies show efficacy in atypical HUS.

Impact:

• Improved understanding of HUS pathogenesis, particularly the role of complement dysregulation and genetic factors, aids in targeted therapy development.
• Enhanced diagnostic approaches and treatment strategies have improved patient survival rates to over 85% at one year.
• Despite advances, chronic renal failure remains a significant sequela (20-65% of cases), and recurrence risk is high in genetic forms, underscoring the need for continued research and therapeutic innovation.