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CMML: between MDS and a myeloproliferative disease | CION Cancer Clinics
CMML, chronic myelomonocytic leukaemia, is a slow cancer of the bone marrow that behaves partly like MDS and partly like a myeloproliferative disease. The marrow makes too many monocytes while red cells and platelets often run low. Some people only need watching; others need medicines or a transplant assessment. Here is what the types, tests and report words mean for you. At CION Cancer Clinics, every leukaemia, MDS and MPN case is reviewed by our haematologist and discussed at a tumour board before a plan is agreed.
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Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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The short answer
What is CMML, in plain words?
CMML, or chronic myelomonocytic leukaemia, is a slow blood cancer of the bone marrow. It sits between two families: MDS, where the marrow makes faulty cells, and myeloproliferative diseases, where the marrow makes too many cells.
Why it has a foot in both camps
In CMML the marrow does both things at once. It makes too many monocytes, a type of white blood cell that normally helps fight infection. At the same time, the red cells and platelets it makes are often too few or badly formed. So one report can show a high white count next to a low haemoglobin and low platelets. That mix confuses many families, because it looks like two different problems.
Why the word leukaemia is in the name
Seeing the word leukaemia is frightening. CMML is not the same as acute leukaemia. It usually moves over months or years, not days. The World Health Organization now groups it with the diseases that overlap MDS and myeloproliferative disease. In some people it changes over time into acute myeloid leukaemia (AML), which is why it is watched closely.
Who tends to get it
It is uncommon and mostly affects older adults, more often men. In most people no cause is found. It is not passed on to children and it is not catching.
This page explains the disease in general. It cannot tell you which type you have or how it will behave in you. Your haematologist reads that from your own marrow and gene reports.Types and groups
Which kind of CMML does my report describe?
Doctors sort CMML in two ways at once: by the pattern of the blood count, and by how many immature cells are present.
The MDS-like type
The total white count is not very high. The main problems are the low counts: tiredness from low haemoglobin, bruising from low platelets and repeated infections.
Your report may say
- MD-CMML or dysplastic type
- Low haemoglobin or platelets
The proliferative type
The white count is high. People more often have an enlarged spleen, night sweats, weight loss and a feeling of fullness under the left ribs.
Your report may say
- MP-CMML or proliferative type
- Splenomegaly, meaning a large spleen
Groups by blast count
Blasts are young, unfinished blood cells. The report may label the disease CMML-0, CMML-1 or CMML-2. A higher group means more blasts and usually closer watching.
If blasts reach 20% of cells, the disease is called AML instead.Gene changes
Most people with CMML have changes in genes inside the marrow cells. These are acquired during life, not inherited. Some of them help your team judge how the disease may behave.
Not sure whether this applies to you?
Ask an oncologistGetting to a diagnosis
How do doctors confirm it is CMML?
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A blood count that keeps showing high monocytes
Often it starts with a routine test. The key finding is a raised monocyte count that stays raised on repeat tests, with monocytes making up at least 10% of the white cells. Laboratory ranges differ, so one result is always read alongside repeat tests and symptoms.
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Ruling out everyday causes
Monocytes also rise with tuberculosis, other long infections and some inflammatory conditions. These are common in India and are checked first, because they need very different treatment.
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A look at the blood under the microscope
A blood smear shows the shape of the cells and whether blasts are present in the blood itself.
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Bone marrow test
A small sample is taken from the hip bone under local numbing. It shows the blast count, how the cells look and whether other blood cancers are present.
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Chromosome and gene tests
The marrow sample is sent for chromosome and gene testing, often to a specialist laboratory. Results can take a while. Together with the blood count, they give a risk score that guides the plan.
On your report
What do the words on a CMML report mean?
- Monocytosis
- A higher than usual number of monocytes in the blood. On its own it does not mean CMML.
- Blasts
- Young, unfinished blood cells. A rising share is one sign the disease is becoming more active.
- Dysplasia
- Cells that look abnormal in shape or size under the microscope.
- CPSS or CPSS-Mol
- A CMML risk score built from your blood counts, blast count, and chromosome and gene results. It groups people from lower to higher risk.
- Hypomethylating agent
- A group of medicines, such as azacitidine and decitabine, that aim to help the marrow make more normal cells.
- Reference range
- The normal band printed by the laboratory. Ranges differ between laboratories, so compare your result with the range on the same report.
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Treatment options
How is CMML treated, and who does each option suit?
Treatment depends on your risk group, your type of CMML, your symptoms and your general health. Not everyone needs treatment straight away.
Watching closely
If your counts are fairly steady and you feel well, your haematologist may suggest regular blood tests and check-ups. This is a real plan, not doing nothing. It spares you side effects while nothing needs fixing. It does not suit someone whose counts are falling or whose symptoms are getting worse.
Controlling counts and symptoms
Blood transfusions can lift a low haemoglobin. Oral medicine such as hydroxyurea may be used to bring down a very high white count or shrink a large spleen. These ease symptoms. They do not change the underlying disease.
Medicines that act on the marrow
For higher-risk disease, or when counts are troublesome, azacitidine or decitabine may be offered. They are given in repeated courses over many months. They can steady the counts in some people, but they do not help everyone.
Stem cell transplant
A donor stem cell transplant is the only treatment that can remove CMML for the long term. It is demanding, and suits a smaller group of fitter patients with a suitable donor. It is done at specialised transplant centres. CION's haematology team reviews your case at a tumour board and can help you understand whether a referral makes sense and what to ask.
Never start, stop or change a medicine or transfusion plan on your own. Your treating team sets it.
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Signs that cannot wait
If you have CMML and develop a fever or shivering, bleeding that will not stop, blood in vomit or stools, sudden severe pain under the left ribs, or breathlessness at rest, go to the nearest emergency department today or call 108. Tell them you have CMML and bring your latest blood report. Do not wait for your next clinic visit.
Commonly believed
What do families often get wrong about CMML?
"A high white count means the infection is bad, so
more antibiotics will fix it."
In CMML the high count comes from the marrow itself, not from an infection. Repeated antibiotic courses will not bring it down. A count that stays high after an infection has settled needs a haematologist to look at it.
"It says leukaemia, so treatment must start
tomorrow."
CMML is usually slow. Many people are watched for a time before any treatment. Taking a few days to complete tests and get the diagnosis right is sensible, not dangerous, unless you have one of the warning signs above.
"If he feels fine, the disease must have gone."
Feeling well is good news, but CMML can change without symptoms. Regular blood tests are how your team notices a change early, so keep the follow-up visits even in good months.
"Our children should be tested because it runs in
families."
The gene changes in CMML develop in the marrow during life. They are not passed from parent to child in the usual way, so family members do not normally need testing for it.
Questions we are asked
Common questions about CMML
Is CMML a type of MDS or a type of leukaemia?
It is both and neither. The World Health Organization places it in an overlap group between MDS and myeloproliferative diseases. It has the faulty cells of MDS and the overproduction of a myeloproliferative disease. That is why you may see it described differently on older reports and websites.
Can CMML turn into acute leukaemia?
In some people, yes. Over time the blast count can rise, and once it reaches the AML threshold it is treated as acute leukaemia. Not everyone goes down this path. Regular blood tests, and a repeat marrow test when something changes, help your team spot it early.
How long can someone live with CMML?
This page cannot give you a number, and a general figure would not describe your own situation. The outlook depends on the risk score, the blast count, the gene results, age and general health. Ask your haematologist to explain your risk group and what it means for you.
My father only has a high monocyte count. Does he have CMML?
Not necessarily. Infections such as tuberculosis, long-standing inflammation and recovery from illness can all raise monocytes. CMML is considered when the rise persists on repeat tests and other causes are ruled out. A bone marrow test is usually needed to confirm it.
Is the bone marrow test very painful?
The skin and bone surface are numbed first. Most people feel pressure and a brief, sharp pulling moment when the sample is drawn. The hip may ache for a day or two afterwards. Tell the team if you are anxious, as they can talk you through each step.
Will he need chemotherapy?
Not always. Some people only need close watching and supportive care. Others are offered tablets to control a high count, or azacitidine or decitabine for higher-risk disease. The choice depends on symptoms, counts and fitness, and your haematologist will explain why a plan suits your family member.
Does CION do stem cell transplants for CMML?
CION's haematology team evaluates the case, presents it at a tumour board and coordinates care with qualified transplant centres when a transplant is being considered. Ask whether you are fit enough, whether a donor is likely and which centre the team recommends.
Is treatment covered by Aarogyasri or insurance?
Parts of the care often are, depending on the scheme and the treatment. Aarogyasri, PM-JAY, CGHS, ECHS, EHS and cashless insurance can all apply. Scheme rules change, so check your current entitlement. Bring your card details and our helpline can check your cover before you travel.
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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
- National Cancer Institute — Myelodysplastic/Myeloproliferative Neoplasms Treatment (PDQ) - Patient Version
- American Cancer Society — Chronic Myelomonocytic Leukemia
- Leukemia & Lymphoma Society — Myelodysplastic Syndromes
- Blood Cancer UK — Understanding blood cancer
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.
Keep reading
Related pages
MDS Explained: When the Marrow Stops Making Good CellsThe wider family CMML overlaps withMDS or Leukaemia: Where the Line IsHow the blast count separates MDS from acute leukaemiaWhen MDS Transforms Into AMLWhat change to watch for and how it is picked upHigher-Risk MDS: Azacitidine and BeyondHow the marrow-acting medicines are givenMyelodysplastic Syndrome (MDS)The full MDS guide
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