Red blood cells carry oxygen to your organs and tissues. These blood cells get created in your bone marrow. That's the soft tissue in the center of your bones. Normally your body breaks down red blood cells when it doesn't need them anymore.

When you have paroxysmal nocturnal hemoglobinuria (PNH), the disease damages new red blood cells and they break apart too soon. Your doctor may use the word "hemolysis" to describe the cells breaking apart. When red blood cells open up, they release hemoglobin, the protein that helps them carry oxygen.

As PNH damages more red blood cells, it can lead to complications like blood clots and anemia. There are treatments you can talk with your doctor about that can stop the breakdown of red blood cells and help keep these complications from happening.

Blood Clots

Clots are sticky clumps that form in your blood. A clot is good when you cut yourself, because it stops the bleeding. But if a clot forms when you don't need it, it could block the flow of blood to your heart or brain, which could be dangerous.

If you have PNH, you can have symptoms like:

  • Pain
  • Swelling
  • Change of skin color
  • Headache
  • Numbness or weakness on one side of your body

If you have any of these things, get medical help right away.


This is a lack of healthy red blood cells to carry oxygen to your organs and tissues. The destruction of red blood cells in PNH causes hemolytic anemia. It's a type of anemia where your body destroys red blood cells faster than it can make new ones.

Symptoms of anemia include:

  • Tiredness
  • Weakness
  • Dizziness
  • Headaches
  • Pale skin
  • Trouble breathing

Many people with PNH have another type of anemia, called aplastic anemia. This is when your body doesn't make enough new blood cells for your body to work normally. People with aplastic anemia get tired and bleed more easily than usual.

Acute Myeloid Leukemia (AML)

In rare cases, PNH can turn into the blood cancer leukemia. It's not clear why this happens.

People with PNH get a type of leukemia called acute myeloid leukemia (AML). It affects the bone marrow and blood. Acute means the cancer comes on quickly. Their bone marrow makes lots of abnormal blood cells that don't work as they should. AML causes a drop in:

  • Red blood cells that carry oxygen
  • White blood cells that protect your body from infections
  • Platelets that help your blood clot

Common symptoms of AML include:

  • Tiredness
  • Pale skin
  • Shortness of breath
  • Sweating
  • More bleeding and bruising than usual


Myelodysplastic Syndromes (MDS)

People with PNH may also have myelodysplastic syndrome (MDS). It's a group of conditions in which your bone marrow doesn't make enough healthy blood cells. People with MDS don't have enough blood cells in their body.

Pulmonary Hypertension

The hemoglobin that red blood cells release can damage blood vessels. Over time, that can lead to pulmonary hypertension -- high pressure in the blood vessels of your lungs. When the blood pressure in your lungs is high, your heart has to work harder to pump enough blood to your body.

Symptoms of pulmonary hypertension include:

  • Tiredness
  • Shortness of breath
  • Dizziness
  • Chest pressure or pain
  • Swelling in the ankles or legs

Pulmonary hypertension can cause long-term problems. So it's important to talk to your doctor if you have symptoms like these.

WebMD Medical Reference

From WebMD

More on PNH