Paroxysmal Nocturnal Hemoglobinuria (PNH)

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired, rare, chronic, and potentially life-threatening blood disease that is associated with persistently low (below normal) hemoglobin levels, thrombosis, and debilitating symptoms. PNH can appear at any age and in any race or gender, and is most often diagnosed in people in their early 30s. 1,2

In PNH, blood cells lack complement regulatory proteins, so the body recognizes these healthy red blood cells as damaged.1 This leads to uncontrolled activation of the complement cascade, initiated at C3, and results in the destruction of oxygen-carrying red blood cells (hemolysis).3 Hemolysis occurs in PNH through two mechanisms: intravascular hemolysis (IVH), which occurs inside blood vessels, and extravascular hemolysis (EVH), which occurs in the liver and spleen.

C5 inhibitors have improved patient survival by addressing IVH, yet despite this, many people with PNH continue to experience ongoing hemolysis and persistently low hemoglobin. According to a retrospective and a cross-sectional study of patients treated with C5 inhibitors, at least 72% had persistently low hemoglobin4,5 and at least 36% required one or more transfusions a year.4

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  1. Paroxysmal nocturnal hemoglobinuria (PNH). The Sidney Kimmel Comprehensive Cancer Center Web site. Accessed November 20, 2019.
  2. Besa EC. Paroxysmal nocturnal hemoglobinuria (PNH). MedScape 2017; Accessed November 20, 2019.
  3. Rosse WF, Ware RE. The molecular basis of paroxysmal nocturnal hemoglobinuria. Blood. 1995;86(9):3277-3286. Accessed November 20, 2019.
  4. McKinley CE, Richards SJ, Munir T, et al. Extravascular hemolysis due to C3-loading in patients with PNH treated with eculizumab: defining the clinical syndrome. Blood. 2017;130(Suppl 1):3471.
  5. Dingli ASH 2020 Abstract/ p.1/ Methods/ ln.1-2; p.2/ Results/ln.7-9; ln.14-15.