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PNH Symptoms

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PNH can cause variety of symptoms. These can vary greatly from person to person. You may have many symptoms, or just one or two. And you may get a new symptom at any point in the course of your illness. The severity and number of symptoms are often related to the size of your PNH clone and how much blood cell destruction is happening.


Hemolysis is the breaking apart of red blood cells. Hemolysis happens when the complement system, a part of your body’s immune system, becomes more active and attacks your PNH red blood cells. The complement is made of small proteins that attack foreign objects, such as viruses and bacteria. Because PNH cells are abnormal, they are seen  as foreign and attacked, causing them to burst.

What are the symptoms of hemolysis?

When your PNH red blood cells break apart, their hemoglobin is released into your plasma. Hemoglobin is the red part of red blood cells. Its carries oxygen around your body. The release of hemoglobin can cause a number of symptoms, including:

  • Dark or tea colored urine, but it does not darken in all cases
  • Low red blood cell count (anemia) which can cause you to:
    • Feel tired
    • Have headaches
    • Have trouble breathing when you exercise
    • Have an irregular heartbeat
  • Muscle spasms in certain parts of your body. This happens when the released hemoglobin binds with nitric oxide and removes it from your blood. Nitric oxide helps your muscles stay smooth and relaxed. When you have a shortage of nitric oxide, you may experience the following:
    • Mild to severe pain in your abdomen or belly area.
    • Spasms in your esophagus which is a "tube" in your throat that goes from your mouth to your stomach; the spasms can make it hard to swallow.
    • Men may have trouble getting or keeping an erection (become impotent).


Thrombosis is a blood clot in a vein. It is often simply called a blood clot. At least 1 out of 3 people with PNH get blood clots. 

Why are blood clots so common for people with PNH?

Scientists are not sure exactly why people with PNH are more likely to get blood clots. But some believe that PNH patients have abnormal platelets that are too "sticky." This means the platelets make clots too easily.

Many people with PNH have a shortage of nitric oxide. Nitric oxide helps prevent blood clots by making it harder for platelets to stick together. Hemolysis – another symptom of PNH – can cause a shortage of nitric oxide.

What are the symptoms of blood clots?

The symptoms of blood clots depend on where the clots occur. People who are otherwise healthy and do not have PNH sometimes get blood clots in the veins of the leg. People with PNH tend to get blood clots in other parts of the body, such as in the brain or abdomen (belly area).

Blood clot in abdomen (belly area)

You may get a blood clot in your abdomen, or belly area. That's the area below your chest and above your hips. Some places in the abdomen where you may get a blood clot include:

  • Your spleen
  • The major vein that leaves your liver; this is called Budd-Chiari syndrome
  • Your intestine (bowel) may not get enough blood; this is called ischemia

Symptoms of getting a blood clot in your abdomen may include:

  • Having fluid and swelling in the belly area; this is called ascites.
  • The area where the clot is may feel warm to the touch.
  • The area where the clot is may be painful.

If the blood clot in your abdomen is not treated:

  • Part of your intestine may die (dead bowel)
  • Your liver may be damaged and stop working

Blood clot in brain

You may get a blood clot in the veins covering your brain. If this happens, symptoms may include:

  • A very bad headache.
  • Trouble speaking, seeing, or moving parts of your body.

Blood clot in skin

You may get a blood clot in the veins of your skin. If this happens, your skin in that area may get red, puffy, warm or painful

Blood clot in arm or leg

You may get a blood clot in the veins of your arm or leg. If this happens that limb may get warm, puffy or painful

Blood clot in lung

Sometimes, a blood clot breaks off and travels to your lung. This is called a pulmonary embolism. If you have a pulmonary embolism, symptoms may include:

  • A sharp pain in your chest; it may get worse when you breathe deeply
  • Trouble breathing (shortness of breath), or you may start breathing fast
  • Suddenly feeling anxious
  • Coughing up some blood
  • Feeling dizzy; you may even faint
  • Sweating a lot

How do I find out if I have a blood clot?

To diagnose a blood clot, your doctor may take pictures of your insides using:

Your doctor may also order a lab test called D-dimer. It is also called Fragment D-Dimer, or Fibrin degradation fragment.

Low Red Blood Cell Count

PNH will mostly cause low red blood cell counts and anemia.  A low red blood cell count is called anemia. If you have a low red blood cell count, you may:

  • Feel a little tired or very tired
  • Feel less alert or have trouble concentrating
  • Have a loss of appetite or lose weight
  • Have paler-than-normal skin
  • Have trouble breathing – shortness of breath
  • Have rapid heartbeat
  • Have difficulty exercising or climbing stairs

Low White Blood Cell Counts

A low white blood cell count is called neutropenia. In general, a low white cell count lowers an aplastic anemia patient’s ability to fight bacterial infections. If you have a low white blood cell count, you may:

  • Have repeated fevers and infections
  • Get bladder infections that make it painful to urinate or make you urinate more often
  • Get lung infections that cause coughing and difficulty breathing
  • Get mouth sores
  • Get sinus infections and a stuffy nose
  • Get skin infections

A fever in an aplastic anemia patient is potentially serious. A doctor should be notified if a fever occurs.

Low Platelet Counts

A low platelet count is called thrombocytopenia. If you have a low platelet count, you may:

  • Bruise or bleed more easily, even from minor scrapes and bumps
  • Get heavier than normal menstrual periods
  • Get nose bleeds
  • Get tiny, flat red spots under your skin (petechiae) caused by bleeding
  • Have bleeding gums, especially after dental work or from brushing your teeth.

If platelet counts are not too low, there may be no obvious symptoms. In rare cases, the number of platelets can get so low that dangerous internal bleeding occurs.

Bleeding that will not stop is a medical emergency. A PNH patient needs to seek immediate medical help if they have bleeding that can’t be stopped by usual methods, such as applying pressure to the area.