The PNH Research and Support Foundation

What is PNH?

PNH is a rare disorder in which red blood cells are prone to destruction by parts of one's own immune system. This happens because the red blood cells are lacking a special protein which normally protects them from being destroyed by the immune system. The destruction of red blood cells (also called “hemolysis”) leads to the release of the red blood cell contents into the blood stream which is responsible for many of the symptoms of the disease.

Because PNH is thought to come from an injury to a blood stem cell (a cell in your bone marrow which produces other cells), PNH can develop in all three types of blood cells — red blood cells which carry oxygen to the body, white blood cells which help fight infections, and platelets which form clots to stop bleeding. While PNH can exist in all blood cell types, the main symptoms caused by PNH are due mostly to the destruction of the red blood cells.

What does PNH stand for?

PNH stands for “paroxysmal nocturnal hemoglobinuria” which means that sometimes there is “hemoglobin” (or part of the red blood cell) in a person’s urine at night. This name is not entirely accurate however. While people with PNH can have hemoglobin in their urine — giving the urine a reddish brown to black color — hemoglobinuria is only seen in about one quarter of patients with PNH at diagnosis. Plus, the destruction of red blood cells does not happen only at night; it occurs all the time. Because the symptoms of PNH vary from patient to patient, it is important for you to work with your doctor to understand all of the symptoms that can occur.

What causes PNH?

Although it is not yet fully known what causes PNH, all patients are less able to produce blood cells. They also have abnormal red blood cells that may be destroyed by their immune system. PNH is a disorder that affects men and women of all races, backgrounds, and ages. Most often, it develops between 20 and 40 years of age. Sometimes people with PNH have other blood disorders such as aplastic anemia (when the body stops making enough red blood cells).

Useful Web Sites

• The PNH Support Group
• The Aplastic Anemia & MDS International Foundation
• PNH Page on AAMDS Web Site
• PNH definition on MedLine/National Institutes of Health