PNH complications: Understanding key hidden risks

Last updated May 27, 2025, by Agata Boxe
Fact-checked by Joana Carvalho, PhD

 

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired disease marked by the destruction of red blood cells, which can lead to symptoms such as dark-colored urine and fatigue.

It is usually caused by mutations in the PIGA gene and may lead to the development of blood clots, kidney damage, and hemolytic anemia, where red blood cells are destroyed more rapidly than they can be replaced.

Knowing what to watch out for with PNH can help you recognize PNH complications early so you can report them to your doctor and get the care you need.

Blood clots

People with PNH are at a higher risk of experiencing thrombosis, or having blood clots form in the body’s blood vessels. There are several factors that may contribute to this, including:

• red blood cells being destroyed inside blood vessels
• activation of platelets, the small cell fragments involved in blood clotting
• defects in the process through which blood clots are normally broken down.

When blood clots arise in people from the general population, they typically form in the veins of the legs. Those with PNH, however, are more likely to develop clots in other areas of the body (as well as in the legs).

The exact symptoms of blood clots in people with PNH depend on their location.

When a blood clot forms in the abdomen, it may cause:

• swelling in the belly area
• warmth to the touch
• pain affecting the area.

If a clot develops in the brain, someone might notice:

• severe headache
• trouble speaking
• vision problems
• mobility issues.

A clot affecting the skin could lead to:

• redness
• puffiness
• warmth
• pain.

Clots in the arms or legs may present with:

• warmth
• puffiness
• pain.

If a clot travels to the lungs, symptoms might include:

• chest pain
• breathing issues
• coughing up blood
• dizziness
• sweating.

Blood clots can significantly impact your long-term health outcomes, as they may lead to organ damage and can be potentially life-threatening for patients with PNH. If you think you may be experiencing symptoms of a blood clot, call 911 or go to the emergency room.

Kidney damage

Potential kidney damage is another PNH health risk. The breakdown of red blood cells caused by the disease releases the oxygen-carrying protein hemoglobin into the bloodstream, which can be toxic to the kidneys. Kidney damage may also occur due to blood clots that may compromise blood supply to the kidneys.

Early warning signs of kidney damage may include:

• urinating less than usual
• confusion
• fatigue
• shortness of breath
• swelling in the legs, ankles, or feet.

Check in with your care team regularly to catch potential kidney problems, as well as other hidden symptoms of PNH. They may recommend tests and other strategies to support your kidney health.

Pulmonary hypertension

Pulmonary hypertension is a disease marked by high blood pressure in the arteries in your lungs, causing your heart to work harder.

With PNH, it can arise as a result of the breakdown of red blood cells and the associated depletion of nitric oxide, a natural vasodilator that causes blood vessels to widen. When nitric oxide levels are low, blood vessels can become narrower, increasing blood pressure.

Pulmonary hypertension can cause symptoms like breathlessness and chest discomfort, which can sometimes be overlooked or misattributed to fatigue, a common symptom of PNH.

It’s important to take these symptoms seriously and let your doctor know if they occur. Your healthcare provider can help determine the cause and suggest an appropriate treatment.

Bone marrow failure

PNH is a rare bone marrow failure disorder where the bone marrow, the soft tissue inside bones where blood cells are produced, fails to function properly. Bone marrow failure can lead to a shortage of platelets, red blood cells, or white blood cells. Its symptoms include:

• fatigue
• bone pain
• unexplained bruising
• headaches
• frequent infections.

Bone marrow failure and the resulting low blood cell counts are problematic because blood cells are involved in many important bodily tasks, such as:

• delivering oxygen
• fighting infections
• helping with blood clotting.

Regular check-ins with your doctor and routine tests can help you keep track of your blood cell count.

Iron deficiency and other nutritional concerns

The chronic destruction of red blood cells due to PNH can cause iron loss and low iron levels in the blood. At the same time, certain treatments, particularly red blood cell transfusions, may cause iron levels to become excessively high.

Due to these issues, it is essential for your doctor to monitor your iron levels through regular blood tests. They may choose to prescribe you iron supplements if needed, but you should not try to self-medicate with them without consulting your provider.

Infections

PNH and certain PNH treatments can affect the immune system, potentially increasing your susceptibility to infections.

Make sure that you are up to date on all recommended vaccinations, which are crucial for protecting your immunity and managing PNH risks. Communicate as needed with your care team and notify them of any changes in your symptoms.

You can also support your immune system by eating a healthy diet rich in vegetables and fruits, exercising regularly, and getting enough sleep.

When to talk to your doctor

Identifying potential complications as soon as possible is crucial for prompt diagnosis and effective treatment. Recognizing and reporting them promptly to your care team can make a difference in managing the long-term effects of PNH.

Try to watch out for signs of potential PNH complications, such as:

• fatigue
• breathing issues
• dark-colored urine
• unexplained bruising.

Keeping a journal of your symptoms and sharing this information with your doctor can be helpful in detecting and recording any concerning changes. Don’t hesitate to advocate for tests or referrals to other specialists if the signs of potential complications persist.

Living with PNH involves the risk of complications that can be hidden, so it is important to stay vigilant. Understanding how PNH affects the body through early recognition, symptom tracking, and communication with your care team can increase the chances of finding the right treatment and helping you feel better.

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PNH News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.