Paroxysmal Nocturnal Hemoglobinuria (PNH)

Medically Reviewed by Jennifer Robinson, MD on September 20, 2023
6 min read

It’s a rare blood disease that stems from your genes. If you have it, your immune system attacks red blood cells in your body and breaks them down. They lack certain proteins that protect them.

You can get paroxysmal nocturnal hemoglobinuria (PNH) at any age. You aren’t born with it. Although it can be life-threatening, treatments can help you feel better and control some of its complications.

The condition affects everyone differently. Some people have only minor problems. For others, it's much more severe. The biggest risk is blood clots. Up to 30% of people with PNH have one at some point.

PNH is caused by a problem with a gene. But you don't get it from your parents, and you can't pass it on to your kids.

A change in a gene, called a mutation, causes your body to make abnormal red blood cells. These cells don’t have proteins that shield them from your immune system. So your body breaks them down. Scientists call this process “hemolysis.”

Some doctors believe PNH is related to weak bone marrow. People with a certain type of anemia, called aplastic anemia, are more likely to get PNH.

The reverse is also true: People with PNH are more likely to get aplastic anemia, though not everyone does. In this condition, your bone marrow stops making new blood cells.

The condition gets its name from one of its symptoms: dark or bright red blood in your urine at night or in the morning. "Paroxysmal" means "sudden," "nocturnal" means "at night," and "hemoglobinuria" means "blood in the urine." It happens in up to 50% of people with PNH.

Symptoms of the disease are caused by:

  • Broken red blood cells
  • Too few red blood cells (which can cause anemia)
  • Blood clots in your veins

You could have many symptoms or just a few. Usually, the more of the faulty blood cells you have in your body, the more the condition will affect you.

Broken red blood cells and anemia may make you:

  • Feel tired and weak
  • Have headaches
  • Feel short of breath
  • Have an irregular heartbeat
  • Have belly pain
  • Have trouble swallowing
  • Have pale or yellowish skin
  • Bruise easily
  • Men may have trouble getting or keeping an erection

The symptoms of blood clots depend on where the clot happens:


  • Red, painful, or swollen area

Arm or leg:

  • Sore, warm, and swollen limb


  • Pain
  • Ulcers and bleeding


  • Bad headache with or without vomiting
  • Seizures
  • Trouble moving, talking, or seeing


  • Trouble breathing
  • Sharp chest pain
  • Coughing up blood
  • Sweating

Blood clots can be dangerous. If you think you may have one, call your doctor right away. Call 911 if you have any trouble breathing or moving, talking or seeing, have a sudden headache, any chest pain, or have a seizure.

Your doctor will ask about your medical history and any symptoms you’ve noticed. They may also ask you:

  • Have you noticed blood in your urine?
  • What medications do you take?
  • Have you had any signs of blood clots?
  • Have you had any stomach or digestive problems?
  • Have you been tested for aplastic anemia or a bone marrow disorder?

You will get routine blood tests. One will count the number of blood cells you have. You will probably also get other tests, such as flow cytometry, which checks whether your red blood cells have the proteins that should protect them.

Your doctor may also check your iron levels or get a sample of your bone marrow. If you have symptoms of a blood clot, they'll use other tests to look for those, too.

You’re probably going to have a lot of things to ask about. Use this list to help you get the information you need.

  • What makes you sure that I have PNH?
  • Do I need any more tests?
  • What is my level of PNH cells?
  • Will I feel differently over time?
  • Are some symptoms more dangerous than others?
  • What can I do to feel better?
  • What are my treatment options?
  • How will they make me feel?
  • How will we know if the treatment is working?
  • Would a bone marrow transplant help me?
  • If so, how do I find a good match for a transplant?
  • Can I take part in a clinical trial?
  • Will I be able to have children?

Most treatments for PNH aim to ease symptoms and prevent problems. Your treatment will depend on how severe your symptoms and disease are.

If you have only a few symptoms from anemia, you may need:

  • Folic acid to help your bone marrow make more normal blood cells
  • Iron supplements to make more red blood cells
  • Eculizumab (Soliris). This drug prevents the breakdown of red blood cells. This can improve anemia, lower or stop the need for blood transfusions, and reduce blood clots. It can make you more likely to get a meningitis infection, so you may need to get a meningitis vaccine.
  • Ravulizumab (Ultomiris). Ravulizumab is virtually identical to eculizumab but has been shown to last longer. Instead of biweekly infusions, patients only need six or seven infusions a year.
  • Pegcetacoplan (Empaveli) is a targeted therapy that can be prescribed for those who are new to treatment or are switching from eculizumab or revulizumab.

Other treatments include:

Blood transfusions. These help treat anemia, the most common PNH problem.

Blood thinners. These medicines make your blood less likely to clot.

Bone marrow stem cell transplant. This procedure is the only cure for PNH. To get one, you’ll need someone healthy, usually a brother or sister, to donate stem cells to replace the ones in your bone marrow. These are not “embryonic” stem cells.

Usually, due to serious health risks, doctors offer a bone marrow transplant only to young people with severe PNH. If your doctor thinks it would work for you, talk with them about the risks and benefits.

If your PNH doesn't get better with usual treatments, you may want to ask your doctor if you can take part in a clinical trial. These research studies try out new ways to treat PNH, before they’re available to everyone. Ask your doctor what’s involved and what you should consider before you sign up.

When you have PNH, it’s even more important to take good care of yourself, so you feel your best.  

Eat a healthy diet. Your body absorbs iron better when you get it with vitamin C. Try combos like iron-fortified cereal with strawberries or spinach salad with orange slices.

Exercise. Fatigue makes it harder to stay active. Ask your doctor what kind of workout is best for you. If your red blood cell count is very low, skip activities that make your heart beat faster, hurt your chest, or strain your breathing.

Protect yourself. Try not to get infections. Wash your hands often, and avoid crowds and sick people. Tell your doctor if you have a fever or feel more tired than usual. Ask if you are up to date on your vaccines.

Get support. Talk with other people who know what you're going through. Ask your doctor about ways to get connected, such as a PNH support group that meets locally or online.

If you’re a woman who wants to get pregnant, talk to your doctor first. PNH can cause problems that make pregnancy risky for you and your baby. If you do become pregnant, your doctors will closely follow how you and the baby are doing.

Tend to your emotions. They’re part of your health, too. It’s OK to feel anger, sadness, or stress after your diagnosis. You may find that it helps to talk with a counselor, especially if those feelings start to affect your daily life. Ask your doctor for a referral.

You may also want to consider joining a support group, where you can talk with other people who understand what you’re going through because they’ve been there, too. Ask your doctor about that, too.

Your friends and family will want to know what's going on with you and what they can do for you. Let them know what would be helpful.

PNH is different for everyone. It's hard to predict if you'll have milder or more serious symptoms, or if you’ll develop other conditions.

The disease can also make you more likely to have other blood-related conditions like aplastic anemia and myelodysplastic syndromes (MDS). MDS is a group of bone marrow diseases in which you have trouble making normal blood cells.

PNH also raises your chances of developing a type of leukemia, a cancer that starts in your bone marrow.

The Aplastic Anemia & MDS International Foundation can help you connect with other people who have PNH and find the services you need.