Paroxysmal nocturnal hemoglobinuria (PNH) is a rare blood disorder affecting red blood cells due to a gene mutation. This mutation causes red blood cells to lack protective proteins, making them vulnerable to complement-mediated destruction, leading to anemia. Symptoms include fatigue, dark-colored urine, and thrombosis risk. Two types of hemolysis occur: intravascular, which destroys red blood cells in the bloodstream, and extravascular, in the liver and spleen. Treatments target the complement system, particularly C3 and C5 proteins, showing improvements in anemia and other symptoms, reducing the need for transfusions.