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What Is Paroxysmal Nocturnal Hemoglobinuria (PNH)?

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare disorder that causes red blood cells to break down sooner than they should. This early destruction can lead to symptoms and complications that range from minimal, such as discoloration of urine, to severe, such as leukemia and stroke. There are no known risk factors for PNH. This condition involves a gene called PIGA, but it’s not a disease you can inherit from your parents. The disease is acquired through genetic mutations that occur throughout your life.

PNH occurs when mutations lead to the loss of the PIGA gene. The mutations happen in what are called “hematopoietic stem cells.” These are cells in your bone marrow that lead to the production of blood cells. If you’ve developed a mutation, then you’ll create abnormal blood cells.

The loss of the PIGA gene means that you lack a protective protein layer on the outside of your red blood cells.

In normal cells, this layer of protein signals to your immune system that the red blood cells aren’t foreign and shouldn’t be destroyed. When you lack these proteins, your immune system breaks apart your red blood cells. If you have PNH, you may have less blood platelets, which are responsible for blood clotting. It’s also likely your platelets will have impaired functioning.

The primary symptom of PNH is discolored urine. Prematurely destroyed red blood cells lead to the release of hemoglobin into your urine. Hemoglobin is what makes your blood red. You can usually see the discoloration at night or early in the morning, after urine has accumulated in your bladder. Some people with PNH, however, won’t see a discoloration. Hemoglobin may be present in your urine at levels that aren’t visible just by looking at the urine.

Other symptoms of having PNH include:

  • back pain
  • a headache
  • shortness of breath
  • abdominal pain
  • bruising easily

A very serious possible complication of PNH is the formation of blood clots. Your platelets are involved in the clotting of your blood, and PNH can decrease or impair your platelets. The symptoms of PNH can vary widely from one person to another. Some people will only have very mild symptoms, while others may experience severe and life-threatening complications.

To diagnose PNH, your doctor will consider your symptoms. The discoloration of urine, unexplained blood clots, and anemia are major clues. You’ll likely need more tests to confirm the presence of the disease.

There are several tests that can confirm the disease, but the best current test is a flow cytometry analysis of red blood cells. The test is very sensitive and can detect the absence of the protein layer on red blood cells. To have the test, you simply need to have a small sample of blood drawn.

Treatment options for PNH vary depending on the symptoms you experience and their severity. For most people, treating the symptoms can successfully manage PNH. Medications that treat anemia minimize the breakdown of blood cells and reduce the risk of blood clot formation. Blood transfusions may be necessary to increase the red blood cell count.

You may require steroids to suppress your immune system as part of the disease management. In this event, your doctor may recommend vaccines to keep you safe from infections. You may also need blood transfusions to keep your blood cell levels normal.

A drug called eculizumab can be very effective in some patients. It stops the breakdown of the red blood cells and may replace the need for blood transfusions.

The lack of the PIGA gene can lead to a host of illnesses and complications that range from minor to life-threatening.


Anemia occurs when you have too few red blood cells. It’s very common with PNH. There can be various causes, but in the case of PNH, it occurs because of the premature destruction of blood cells. The symptoms include:

  • fatigue
  • weakness
  • headaches
  • lightheadedness
  • pale skin
  • shortness of breath

Acute Myeloid Leukemia

Less commonly, PNH can lead to acute myeloid leukemia. The symptoms include:

  • bleeding gums
  • bruising
  • a fever
  • shortness of breath
  • weight loss
  • skin rashes
  • bone pain
  • fatigue


The most serious possible complication, although not as common as anemia, is the formation of blood clots. This complication is known as thrombosis. Clots cause pain and soreness where they form in the body. They can also move throughout the body. Blood clots in the lungs, brain, or near the heart can result in stroke and death.

The outlook for someone with PNH varies depending on the severity of the illness. In very few cases, the abnormal blood cells will decrease over time. In most cases, however, treatment is necessary to manage the disease. Most people live 10 years or more after the initial diagnosis.