Overview of Paroxysmal Nocturnal Hemoglobinuria

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Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired blood stem cell disorder. It was originally named for its symptom of dark-colored urine (hemoglobinuria) produced in the morning. It was thought that the abnormal breakdown of red blood cells (hemolysis) that caused the dark urine occurred in bursts (paroxysms) that occurred at night. Research has shown, however, that the hemolysis in PNH, caused by a biochemical defect, occurs throughout the day and does not occur in bursts. The change in urine color may occur at any time but is most dramatic in concentrated nighttime urine.

Improved understanding of paroxysmal nocturnal hemoglobinuria has redefined the disorder as having hemolysis, blood clots in veins (thrombosis), and a deficiency in the production of all types of blood cells (hematopoiesis). PNH affects both males and females of all ethnic backgrounds and may occur at any age, but is most commonly found among young adults.


Many people with PNH do not have symptoms. Symptoms of PNH depend upon whether hemolysis, thrombosis, or deficient hematopoiesis is present.

  • Hemolysis - cola-colored urine (hemoglobinuria), hemolytic anemia
  • Thrombosis - where the clot occurs determines the symptoms. If the clot is located in a vein of the liver, there may be jaundice and an enlarged liver. In the abdomen, a clot would cause abdominal pain; in the head, a headache. Clots in the skin cause raised, painful, red lumps over large areas of the skin, such as the back.
  • Deficient hematopoiesis - anemia (not enough red blood cells), susceptibility to infections (not enough white blood cells), and abnormal bleeding (not enough platelets).


There are several laboratory tests which can help diagnose of paroxysmal nocturnal hemoglobinuria. The most precise is testing the blood to detect CD55 and CD59, two proteins. Absence of these proteins on red blood cells confirms the diagnosis of PNH. During diagnosis, other blood tests will be done including a complete blood cell count (CBC), reticulocyte count, serum lactate dehydrogenase (LDH), bilirubin, and haptoglobin. A bone marrow sample (biopsy) may be taken and examined under a microscope.


Treatment is based upon which symptoms are present. Many adults are treated with steroids (prednisone) daily when hemolysis occurs and changed to alternate days during remission. Iron and folic acid supplements help replace losses due to hemolysis. Some individuals may receive androgenic hormones to stimulate red blood cell production. In severe anemia, a blood transfusion may be necessary. Blood thinners may be used to reduce the development of blood clots. Deficient hematopoiesis may be treated with antithymocyte globulin (ATG).

A bone marrow (stem cell) transplant can replace the defective blood cells in PNH with normal ones. Nearly all individuals with PNH will eventually require a transplant in order to live longer. If the transplant is done late in the course of the disease the results are not as good because the individual is very sick by that time.

First Drug for PNH Approved

On March 16, 2007, the U.S. Food and Drug Administration (FDA) approved Soliris (eculizumab) for the treatment of PNH. The approval was based on the results of several studies that showed treatment with eculizumab produced a dramatic reduction in hemolysis, and the days of hemoglobinuria each month decreased.

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