The role of complement inhibition in PNH.

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, chronic, debilitating, acquired disorder that most frequently presents in early adulthood and usually continues throughout the life of a patient. PNH results in the death of approximately half of affected individuals, mainly through thrombotic complications, and until recently had no specific therapy. In 2007 eculizumab, an anti-complement antibody targeting the C5 complement component was approved for PNH by both the US Food and Drug Administration (FDA) and the European Medicines Agency (EMEA). Eculizumab is very effective in the treatment of intravascular hemolysis and all its sequelae, which include most of the symptoms and complications of PNH. Eculizumab has revolutionized our approach to hemolytic PNH and as it markedly reduces the principal complications of PNH, namely thrombosis and renal failure, should have a significant impact on survival. However, the development of eculizumab presents new challenges in PNH, such as how to avoid complications of therapy, how to overcome some of the problems associated with treatment and who to select for treatment, as only a proportion of patients with a PNH clone will benefit. This article will review the evidence behind the use of eculizumab in PNH, the effect it will have on the complications of the disease, the most appropriate selection of patients for therapy, the optimal management and the potential complications of the therapy.