• PNH overview
  • Who gets PNH?
  • The associated risks
  • Signs and Symptoms
  • Diagnosis
  • What to expect with PNH
  • Living with PNH
  • Communicating about PNH
  • Resources and links
  • References

What is Paroxysmal Nocturnal Haemoglobinuria (PNH)?

PNH is an acquired disease that destroys an important part of the blood, the red blood cells.1 Red blood cells develop in the bone marrow and are important because they help deliver oxygen.

With PNH, some or all of the body’s red blood cells (RBCs) are destroyed in a process called ‘haemolysis.’ In PNH, haemolysis is taking place at all times and at high rates, putting people with PNH at risk. Haemolysis is the main cause of the symptoms with PNH.1-4

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Haemolysis is the cause of the symptoms of PNH, including the most serious complications.1
When red blood cells burst, they release haemoglobin, a protein responsible for carrying oxygen in the blood. While haemoglobin is good for the body while inside the red blood cell, it causes harm when it's outside the cell. Over time the build-up of free haemoglobin can cause serious health problems.1

The measurement of haemolysis - LDH
Lactate dehydrogenase (LDH) is a molecule inside red blood cells that, can be measured in a blood test and provides a guide to the rate of haemolysis taking place. A high LDH measure indicates that a large number of red blood cells have been destroyed. For people with PNH, regular measurement of LDH is important.5

Who gets PNH?

  • PNH is a very rare, acquired disease6
  • PNH can be found in people of all ages but is diagnosed most commonly among people in their early 30s7
  • PNH is an acquired disease, meaning that it develops over time1,4
  • PNH is not an inherited disease1,4
  • Importantly PNH is not contagious or infectious1,4
  • People with certain bone marrow diseases are at increased risk of developing PNH8,9
  • The diseases aplastic anaemia (AA) and myelodysplastic syndrome (MDS) reduce the production of red blood cells and increase a person's risk of developing PNH
  • The family members of a person with PNH are not at increased risk of PNH1,4

There are serious risks associated with PNH

A major concern with PNH is that its effects are not always noticeable, so serious health risks can occur without warning.If left untreated, PNH can lead to:

  • Blood clots: These form when parts of blood clump together. Blood clots can block veins and arteries and lead to heart attack, stroke and other problems, because clots may form in any part of your body10,19
  • Kidney damage: About 2/3 of people with PNH have kidney disease12
  • Lung Problems: Can be caused by pulmonary hypertension. This can lead to shortness of breath and other serious health problems20

"PNH" stands for Paroxysmal Nocturnal Haemoglobinuria

The disease was called this before much was known about it. Today, although more is known about the disease, doctors still call it PNH.3

But the name is a little misleading! Here’s why:

  • Paroxysmal: This word implies the disease “comes and goes”. But we now know that PNH is always present and haemolysis is always happening, whether or not you are experiencing symptoms3
  • Nocturnal: The effects of PNH don’t just happen at night – they happen all the time3
  • Haemoglobinuria: This word means haemoglobin found in urine (making it a darker colour) and implies that this is the main symptom of PNH. In fact, not everyone with PNH has dark-coloured urine when diagnosed, although most people will experience it at some point3

Signs and Symptoms

The signs and symptoms of PNH can be silent and unpredictable. They affect each person differently and can change from day to day. Fatigue, often severe, is a common symptom of PNH.21 

PNH is like an iceberg – what can not be seen or felt can be the most damaging21

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Someone with PNH may experience one or more of the symptoms listed above frequently or just occasionally. However, they may not immediately experience other complications such as blood clots and kidney disease.


Due to the wide range of symptoms associated with PNH, it is not unusual for months or years to pass before the correct diagnosis is established.17

How is PNH diagnosed?
PNH is diagnosed by a special test called ‘Flow Cytometry’.16 Doctors apply this test to a sample of blood to find out whether blood cells are affected by PNH.

What is clone size?
Clone size refers to the percentage of red blood cells affected by PNH. The larger the clone size, the greater the number of red blood cells that are affected. However, even small clone sizes can lead to PNH-related health symptoms.14

Early diagnosis is important in reducing the rate of haemolysis16,18
Reducing haemolysis as soon as possible may help in limiting the damage it can cause.16,18

Fortunately much has been learnt about PNH in recent years and there have been advances in treatment options. These new discoveries have helped doctors and people with PNH proactively manage the disease, and helped people with PNH return to normal life.10

What you can expect

If you have been diagnosed with PNH you can expect close, lifelong medical attention and support. Your GP and haematologist are key to ongoing care. Other medical professionals, such as nurses, are often involved too. To help ensure that the best care is provided at all times, you will need to keep in close contact with your medical team, alerting them promptly to any changes in health.

Treatment decisions are based on your symptoms, the extent of any organ damage and the results of regular monitoring for signs of the disease.

Anticoagulants may be prescribed to reduce the risk of blood clots. Anticoagulants have no effect on the haemolysis that causes the symptoms of the disease.15

Blood transfusions may be given to help restore a healthy level of red blood cells. Blood transfusions do not treat the haemolysis, that causes the symptoms of the disease.15

Treatment advances

Better understanding of the dysfunction underlying PNH has led to the development of treatment that addresses the underlying cause of the disease.6,19

Tracking PNH

There are a number of important regular blood tests that can help show how well PNH is being controlled.

  • LDH: Frequent testing of LDH is important as it provides a guide to the rate of haemolysis that is taking place.5 By tracking LDH levels over time, it is possible to see how well the disease is being managed
  • Red blood cells: These cells deliver oxygen and remove waste from the body. Red blood cells are affected by PNH so tests are important for checking that levels are healthy
  • Haemoglobin: This is the part of the red blood cell that carries oxygen around the body. Low levels can cause anaemia, leading to feelings of tiredness and weakness. Anaemia is a common symptom of PNH, so tests help doctors see how well PNH is being managed
  • White blood cells: These protect the body from infection. White blood cells can be affected by PNH, so tests are important for checking that levels are healthy

Regular visits to the GP are important for monitoring general health and visits to a haematologist every three to six months are recommended.

Living with PNH

PNH is a serious disease and living with it can be stressful. Understanding the disease can help in the management of signs and symptoms. Keeping track of symptoms is important.

  • Track the signs and symptoms: Your doctor should be informed of any change in health, even if it may not be related to PNH
  • Making changes in day-to-day living can help make life easier for people with PNH. The fatigue that some people with PNH experience means that they become exhausted easily, so reducing the number of daily tasks, and streamlining them where possible, is important

Living with PNH can be difficult as the disease is serious, but often silent. Here are some suggestions that may make day-to-day living easier.

  • Keeping a journal of symptoms can be useful as it may reveal links between general health and the degree of haemolysis
  • A doctor should be aware of all medications being taken – prescription and non-prescription
  • A doctor should be notified of any invasive procedures (eg, dental work, surgery) that are planned
  • People with PNH often have other health problems, including bone marrow disorders affecting the blood so it is important that overall health is monitored regularly
  • Seeking help. Asking for help, when it’s needed, is essential.

The following section offers tips that may help you to talk about PNH to family and friends.

Talking to others about PNH

Talking about your disease may help make life easier. For people who have been diagnosed recently, here’s why talking to others about PNH might be important.

  • Understanding: PNH can cause severe fatigue which can be frustrating and upsetting for the person involved. It can be helpful for others to understand that the fatigue is part of the disease and, with help and some lifestyle changes, can often be managed
  • Emotional support: Family and friends of someone with PNH can provide valuable help and support in managing everyday life and dealing with the emotional impact of the disease
  • Information: Family and friends generally welcome information about PNH. Websites, such as this, can help answer their questions

Resources and links

PNH Support Association of Australia Inc. (PNHSAA)
The association’s aim is to support PNH patients and their loved ones to manage their condition positively by providing access to accurate information, practical resources and a support network. They also provide opportunities to meet with other patients and caregivers to reduce the isolation often experienced by people with rare diseases.

Rare Voices Australia (RVA)
RVA is a national organisation is an advocate on behalf of people who live with a rare disease. RVA works with governments, researchers, clinicians and industry to promote research, diagnosis, treatment and services for all rare diseases in Australia.

PNH Symptom Tracker

Click here to download the PNH Symptom Tracker.


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  2. 2. Rother RP, et al. JAMA. 2005;293:1653-1662.
  3. 3. Rosse WF. Paroxysmal nocturnal hemoglobinuria. In: Hoffman R, et al, eds. Hematology: Basic Principles and Practice. 3rd ed. New York, NY: Churchill Livingstone; 2000:331-342.
  4. 4. Brodsky RA. Paroxysmal nocturnal hemoglobinuria. In: Hoffman R, et al, eds. Hematology: Basic Principles and Practice. 4th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2005:419-427.
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  13. 13. Hill A, et al. Br J Haematol. 2007:137:181-192.
  14. 14. Urbano-Ispizua A, et al. In: Abstracts of the 15th Congress of the European Hematology Association; June 10-13, 2010; Barcelona, Spain.
  15. 15. Rachidi S, et al. Eur J Intern Med 2010;21:260-267.
  16. 16. Borowitz , et al. Cytometry Part B, 2010;78B:211-230.
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