Complement-driven anemia: more than just paroxysmal nocturnal hemoglobinuria

Area of Science:

• Immunology
• Hematology
• Nephrology

Background:

• Atypical hemolytic uremic syndrome (aHUS), hemolysis, elevated liver function tests, and low platelets syndrome (HELLP), and transplant-associated thrombotic microangiopathy share genetic links to complement dysregulation.
• Paroxysmal nocturnal hemoglobinuria (PNH) is a hematopoietic stem cell disease with PIGA mutations, leading to complement-sensitive erythrocytes.
• Complement activation on endothelial surfaces causes damage, platelet consumption, and hemolytic anemia in thrombotic microangiopathies.

Purpose of the Study:

• To review the pathophysiology of complement-mediated disorders like aHUS and PNH.
• To discuss the role of complement inhibitors, such as eculizumab, in treating these conditions.
• To highlight emerging complement-targeting therapies.

Main Methods:

• Literature review of genetic mutations in complement regulatory genes.
• Analysis of the mechanism of complement activation in thrombotic microangiopathies.
• Review of clinical data and preclinical studies on complement inhibitors.

Main Results:

• Germline mutations in alternative complement pathway (APC) genes are common in aHUS, HELLP, and TMA.
• Variable penetrance of these conditions is influenced by superimposed inflammatory processes.
• Eculizumab effectively inhibits terminal complement, treating aHUS and PNH by blocking C5 cleavage.

Conclusions:

• Complement dysregulation is a key factor in aHUS, HELLP, and PNH pathogenesis.
• Eculizumab represents a significant therapeutic advance for these complement-mediated diseases.
• Next-generation complement inhibitors show promise for broader applications in complementopathies.