What is PNH?

PNH is a rare and serious acquired disease which causes red blood cells to break apart. Red blood cells are important because they help deliver oxygen and remove waste from your body.

PNH is thought to come from a change (also known as a mutation) in a specific gene, called the PIG-A gene. Patients with PNH develop a large number of abnormal PNH blood and marrow cells with this gene mutation. This group of cells is called the “PNH clone”. 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. This destruction (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. However, PNH can cause different symptoms in different people.

What does PNH stand for?

PNH stands for “paroxysmal nocturnal hemoglobinuria”. Paroxysmal means sudden and irregular. Nocturnal means at night. Hemoglobinuria means hemoglobin in the urine. Hemoglobin is the red part of red blood cells. A person with PNH may have episodes of dark urine in the morning, but this symptom is not present in all PNH patients. 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.

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