Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Paroxysmal nocturnal hemoglobinuria ?
    ### Response:
    Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired disorder that leads to the premature death and impaired production of blood cells. It can occur at any age, but is usually diagnosed in young adulthood. People with PNH have recurring episodes of symptoms due to hemolysis, which may be triggered by stresses on the body such as infections or physical exertion.
    