Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hemolytic anemia with 
highly variable clinical symptoms making the diagnosis and prediction of its 
outcome difficult. It is caused by the expansion of a hematopoietic progenitor 
cell that has acquired a mutation in the X-linked phosphatidylinositol glycan 
class A (PIGA) gene that results in deficiency of the 
glycosylphosphatidylinositol anchor structure responsible for fixing a wide 
spectrum of proteins particularly CD55 and CD59. The clinical features of this 
disease arise as a result of complement-mediated hemolysis in unprotected red 
cells, leukocytes, and platelets as well as the release of free hemoglobin. 
Patients may present with a variety of clinical manifestations, such as anemia, 
thrombosis, kidney disease, smooth muscle dystonias, abdominal pain, dyspnea, 
and extreme fatigue. PNH is an outstanding example of how an increased 
understanding of pathophysiology may directly improve clinical symptoms and 
treat disease-associated complications when we inhibit the terminal complement 
cascade. This topic will discuss PNH overview to assist specialists looking 
after PNH patients.