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PNH and its overlap with aplastic anaemia | CION Cancer Clinics
A PNH clone is common in aplastic anaemia, and a small one usually causes no symptoms. PNH cells lack a protective coating, so they survive the immune attack on the marrow. If the clone grows, it can break down red cells and cause blood clots. This page explains the test, the report words, the warning signs and when treatment changes, and what it cannot tell you about your own result. At CION Cancer Clinics, our haematologist cares for anaemia, bleeding, clotting and inherited blood disorders, with ArogyaSri, CGHS and cashless insurance accepted.
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Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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On this page
- What is PNH, and why is it tested for in aplastic anaemia?
- What can the overlap look like in real life?
- How is a PNH clone found and measured?
- What do the words on a PNH report mean?
- Does finding a PNH clone change the treatment plan?
- What do families often get wrong about PNH?
- Common questions about PNH and aplastic anaemia
The short answer
What is PNH, and why is it tested for in aplastic anaemia?
PNH, short for paroxysmal nocturnal haemoglobinuria, is a condition where some blood cells are missing a protective coating, so the body's own defences break open red cells. It is checked in aplastic anaemia because the two often appear together. Many people with aplastic anaemia, a condition where the bone marrow stops making enough blood cells, carry a small group of these PNH cells.
Why the two turn up together
In aplastic anaemia the immune system is thought to attack the marrow. Cells that lack the coating seem to be passed over by that attack. So while normal marrow cells are lost, the PNH cells survive and make up a larger share of what is left. This group of cells is called a PNH clone.
What a clone does and does not mean
Finding a clone does not mean you have a second serious illness. Many clones stay small and cause no trouble at all. A larger clone can start to break down red cells and raise the risk of blood clots. That is why your team watches its size over time rather than acting on one result.
This page cannot tell you what your own clone size means. Your haematologist reads it alongside your blood counts and symptoms.How it shows itself
What can the overlap look like in real life?
People with both findings tend to fall into a few broad pictures. Which one you are in shapes what your team does next.
A clone found only on the test
The marrow failure is the main problem. The PNH cells are few, cause no symptoms, and show up only because the lab looked for them.
What usually happens
- Treatment focuses on the aplastic anaemia
- The PNH test is repeated from time to time
Red cells breaking down
The clone is large enough to destroy red cells inside the blood vessels. You may notice dark, cola-coloured urine, often first thing in the morning, along with tiredness and yellow eyes.
Blood clots in unusual places
PNH can cause clots in the veins of the tummy, liver or brain, not only in the legs. This is the most serious part of the condition and the main reason clone size is tracked.
Swallowing and tummy pain
When red cells break down, the gut muscles can go into spasm. Some people have pain on swallowing, tummy cramps or erection problems during these spells.
Not sure whether this applies to you?
Ask an oncologistThe test
How is a PNH clone found and measured?
A plain blood sample
No bone marrow sample is needed for this part. Blood is taken from a vein in the arm, the same way as for a routine blood count. No fasting is required.
Flow cytometry in a specialist lab
A machine checks thousands of single cells for the missing coating proteins. Not every lab offers this test, so the sample may be sent to a reference laboratory, which can add a few working days.
The clone size on the report
The result gives the share of red cells and white cells that lack the coating, usually as a percentage. The white cell figure is often the more reliable guide, because red cells from a transfusion can dilute it.
Repeat checks over time
A clone can grow, shrink or disappear. Your haematologist will usually repeat the test at intervals, and sooner if new symptoms appear.
On your report
What do the words on a PNH report mean?
- PNH clone
- A group of blood cells that all come from one marrow cell and all lack the protective coating.
- GPI-anchored proteins, CD55, CD59
- The names of the coating proteins the lab looks for. Missing CD59 is what leaves red cells open to attack.
- FLAER
- A marker used in the test to spot white cells that lack the coating. It helps the lab measure small clones accurately.
- Haemolysis
- Red cells breaking open. On a report it shows as a raised LDH and bilirubin, with a low haptoglobin.
- LDH
- An enzyme released when cells break. A high level is one sign that a PNH clone is destroying red cells.
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Signs of a clot that cannot wait
If you have PNH cells and develop sudden severe tummy pain, a swollen painful leg, a sudden severe headache, sudden breathlessness or chest pain, go to the nearest emergency department now or call 108. Tell them you have PNH and aplastic anaemia. Do not wait for your next clinic visit, and do not take any medicine on your own first.
Treatment
Does finding a PNH clone change the treatment plan?
Often it does not, at least at first. If the clone is small and causes no symptoms, the marrow failure is treated in the usual way. Immune-calming treatment such as ATG, or a stem cell transplant, remains the main decision.
When the PNH itself needs treating
If red cells are breaking down heavily or a clot has happened, doctors may use a complement inhibitor. These medicines, such as eculizumab and ravulizumab, block the part of the immune system that breaks the red cells. They reduce the breakdown but do not fix the marrow. They also raise the risk of meningitis, so vaccines and sometimes preventive antibiotics are arranged first.
Who these medicines do not suit
They are not used for a small clone with no signs of breakdown. They do not help low counts caused by marrow failure. They are also costly and access varies, so ask your team whether a scheme or insurer will cover them.
Where transplant fits
A stem cell transplant is the one treatment that can replace both the failing marrow and the PNH cells. It carries serious risks and is done at specialist transplant centres. CION's haematology team reviews your case at a tumour board and helps you reach one.
Commonly believed
What do families often get wrong about PNH?
"PNH means the aplastic anaemia has turned into cancer."
PNH is not a cancer. It is an acquired change in some blood cells, and it does not spread to other organs. It is serious because of red cell breakdown and clots, and it needs regular follow-up, but it is a different thing from leukaemia.
"It only happens at night, so daytime symptoms are something else."
The name comes from dark urine noticed in the morning. Red cell breakdown can happen at any time of day, and many people never see dark urine at all. Report tiredness, yellow eyes or tummy pain whenever they happen.
"Our child will pass PNH on to their children."
PNH is not inherited. The change happens in a marrow cell during life, not in the genes a parent passes down. Brothers, sisters and children are not at raised risk because of it.
"A small clone today means nothing to watch."
Most small clones stay small, but some grow, especially after the marrow recovers with treatment. That is why repeat testing matters even when you feel well.
Questions we are asked
Common questions about PNH and aplastic anaemia
My report says a small PNH clone was found. Should I be worried?
A small clone is common in aplastic anaemia and often causes no problems. Some doctors see it as a sign that the marrow failure is immune-driven, which can help in planning treatment. It still needs watching, because clones can grow. Ask your haematologist when the test will be repeated and which symptoms to report.
Can PNH come first and aplastic anaemia later?
Yes. Some people are diagnosed with PNH because of dark urine or a clot, and their blood counts fall later as the marrow fails. Others start with aplastic anaemia and develop signs of PNH after treatment. This is why both conditions are looked for whenever one is found, and why follow-up continues for a long time.
Is the PNH test the same as a bone marrow biopsy?
No. The PNH test uses an ordinary blood sample from the arm. A bone marrow biopsy, where a small piece of marrow is taken from the hip bone, is a separate test used to diagnose aplastic anaemia itself. Most people with suspected aplastic anaemia will be asked to have both.
Why is dark urine important?
Dark, cola-coloured urine can mean red cells are breaking down inside the blood vessels. It is one of the clearest signs that a PNH clone has become active. Note when it happens and tell your haematology team soon. If it comes with tummy pain, a swollen leg or breathlessness, go to the emergency department.
Will I need blood thinners?
That depends on your clone size, whether you have had a clot, and how low your platelets are. Low platelets make blood thinners riskier, so the decision is a careful balance. Only your treating team can set this. Never start or stop a blood thinner on your own.
Can ATG treatment make PNH worse?
The clone may grow after immune-calming treatment, as normal marrow cells and PNH cells both recover. For most people this does not cause symptoms, but it is one reason the PNH test is repeated after treatment. A clone is not usually a reason to avoid ATG. Your haematologist will explain how it affects your own plan.
Does CION do the PNH test and treatment?
CION's haematology team reviews your reports, arranges the right tests through accredited laboratories and discusses your case at a tumour board. Where a transplant or specialist medicine is needed, the team coordinates access with qualified centres. Bring every blood report and any earlier PNH result to your first appointment.
Can a pregnant woman with PNH be looked after safely?
Pregnancy raises the risk of clots, and PNH adds to it. It needs planning with a haematologist and an obstetrician who work together, ideally before pregnancy begins. Do not change any medicine on your own if you find you are pregnant. Tell your haematology team straight away so they can review the plan.
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Dr. Basudev Pokhrel reviews blood counts, transfusion needs and blood disorders, and works with the CION tumour board on blood cancers.
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Sources
- NHLBI — Paroxysmal Nocturnal Hemoglobinuria
- NHLBI — Aplastic Anemia
- NHS — Aplastic anaemia
- American Society of Hematology — Blood disorders for patients
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
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