Paroxysmal nocturnal hemoglobinuria (PNH) is a rare disorder that causes red blood cells to break down. This can lead to symptoms and complications ranging from discoloration of urine to leukemia and stroke.

There are no known risk factors for PNH. This condition involves a PIGA gene named for the phosphatidylinositol glycan class A gene. But it’s not a disease that’s inherited from your parents. The disease is acquired through genetic mutations.

PNH occurs when mutations lead to losing the PIGA gene. The mutations happen in what are called hematopoietic stem cells. These are cells in your bone marrow that lead to blood cell production. Your body will create abnormal blood cells if you’ve developed a mutation.

Losing the PIGA gene means you lack the protective protein layer outside your red blood cells. In normal cells, this protein layer signals to your immune system that the red blood cells are not foreign and should not be destroyed.

When you lack this protein, 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 not function properly.

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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.

However, some people diagnosed with PNH will not see any discoloration in their urine. Hemoglobin may be present in your urine at levels that are not visible when just looking at the urine.

Other PNH symptoms include:

Blood clots are a serious risk.

PNH symptoms 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.

Paroxysmal (sudden, recurring) episodes of excess hemoglobin in the body define PNH. Stressors like the following examples can be triggers:

To diagnose PNH, your doctor will consider your symptoms. Major clues include the discoloration of urine, unexplained blood clots, and anemia. Your doctor will likely order more tests to confirm the presence of the disease.

Several tests 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. For the test, a healthcare professional will draw a small blood sample.

Tests can determine whether PNH is occurring alongside a bone marrow disorder.

PNH treatment options 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.

Steroids to suppress your immune system can be part of the disease management. In this event, your doctor may recommend vaccines to protect you against infections.

A biologic drug called eculizumab can be very effective in some patients. It blocks what is known as the C5 pathway, which stops the breakdown of red blood cells. Eculizumab may replace the need for blood transfusions.

Blood transfusions

Blood transfusions have been a common option for treating the breakdown of red blood cells and iron deficiency in people diagnosed with PNH. Medications to prevent blood clots are typically given alongside transfusions.

Blood transfusions may be necessary to increase the red blood cell counts in response to certain medications.

Bone marrow transplant

People diagnosed with high risk PNH who have an associated bone marrow disorder may be offered bone marrow transplants. The donor may be a sibling or person who provides a close match. In the best cases, the transplant can eliminate PNH.

People lacking the PIGA gene are at risk of certain 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, anemia occurs because of the premature destruction of blood cells.

Acute myeloid leukemia

Less commonly, PNH can lead to acute myeloid leukemia(AML). AML is a type of cancer that affects the bone marrow and blood. It is also sometimes referred to as acute myelogenous leukemia and acute non-lymphocytic leukemia.


The most serious possible complication of PNH 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.

Below are frequently asked questions relating to PNH.

What is the main cause of paroxysmal nocturnal hemoglobinuria?

The main cause of PNH is variations in the PIGA gene in hematopoietic stem cells.

What are the signs and symptoms of PNH?

The primary symptom of PNH is bloody or discolored urine. The condition can also cause anemia, blood clots, fatigue, and shortness of breath.

How do you treat paroxysmal nocturnal hemoglobinuria?

The main treatments for PNH are medications, blood transfusions, and bone marrow transplants. The right treatment will depend on the severity and symptoms of each case.

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. However, in most cases, treatment is necessary to manage the disease.

The development of a newer biologic treatment, eculizumab, has improved the outlook for people for whom other treatments have failed. The life expectancy for people with PNH may now be the same as those who do not have the condition.