Acute Promyelocytic Leukaemia (APL)

APL is rare type of acute myeloid leukaemia (AML). It is also called APML or AML M3. 

Blood cells and leukaemia

To understand how and why leukaemia affects you as it does, it helps to know how you make blood cells.

Your body makes blood cells in the bone marrow. The bone marrow is the soft inner part of your bones. You make blood cells in a controlled way, as your body needs them.

All blood cells start as the same type of cell, called a stem cell. This stem cell then develops into:

  • myeloid stem cells become white blood cells called monocytes and neutrophils (granulocyte), red blood cells and platelets
  • lymphoid stem cells, which become white blood cells called lymphocytes

The diagram below helps to explain this.

A simplified diagram showing how blood cells are made

In acute myeloid leukaemia, the bone marrow makes too many monocytes or granulocytes. These cells are not fully developed and are not able to work normally.

Diagram showing the cells in which AML starts

Symptoms and diagnosis

In APL, the levels of red blood cells, white blood cells, and platelets are low. This is called pancytopenia. This can cause:

  • infections
  • tiredness
  • bruising and bleeding

You may also have some weight loss. 

Your GP would usually arrange for you to have a blood test if you have these symptoms. They may then refer you to a specialist if your blood test results are abnormal. This is usually a specialist in blood disorders (a haematologist). 

Your specialist will take a sample (biopsy) of your bone marrow. They look at the cells under a microscope to check for leukaemia cells. 


APL can develop very quickly so you will start treatment straight away. Treatment aims to get rid of all signs of APL (remission).

The main treatment for APL is tretinoin (also called ATRA or all-trans-retinoic-acid). Tretinoin belongs to a group of drugs called retinoids, they are similar to vitamin A.  You take tretinoin as tablets. You might start taking this if your doctor suspects that you have APL. Treatment often starts before all of your test results are back.

If you start treatment and your diagnosis changes after further tests, you will stop taking tretinoin. The tretinoin you have already taken will not do any harm.

You have tretinoin with either:

  • a chemotherapy called an anthracycline (such as idarubicin or daunorubicin)
  • arsenic trioxide

You have some of these drugs into a vein (intravenously) and some as tablets. Your healthcare team can explain this to you in more detail.

If APL comes back

If your APL comes back (relapses), you usually have more treatment. This depends on treatment you have already had. For example, if you had tretinoin with arsenic trioxide as your first treatment, you might have tretinoin with chemotherapy. If you had tretinoin and chemotherapy, you might have tretinoin and arsenic trioxide.

Some people may have a stem cell transplant. A transplant allows you to have high doses of chemotherapy. The transplant of healthy stem cells find their way back to your bone marrow where they start making blood cells again. Your bone marrow can then slowly recover.

Supportive therapies 

You may need treatment to relieve symptoms, rather than treat your APL. For example, you might need transfusions. You have a drip containing red blood cells if the level of your red blood cells is low. If your platelets are low, you have a drip of a clear fluid containing platelets.

Research and clinical trials

Researchers continually look for ways to improve treatment. There may be fewer clinical trials for rare sub-types of leukaemia such as APL. But you can ask your healthcare team if there is anything suitable for you.  

A large group of researchers in the UK are carrying out a series of trials for people with AML. This includes people with APL.

The AML 19 trial is following people with APL who are having treatment with tretinoin and idarubicin. As well as looking at the results of treatment, it is also asking people about their quality of life.


Coping with a diagnosis of cancer can be difficult, both practically and emotionally. Being well informed about your cancer and its treatment can make it easier to make decisions and cope with what happens.

Talking to other people who have the same thing can also help. As APL is rare, you may not meet other people with exactly the same type of AML to you. In this situation national organisations and their forums might be useful.

Our discussion forum Cancer Chat is a place for anyone affected by cancer. You can share experiences, stories and information with other people who know what you are going through.

Blood Cancer UK have information about APL, as well as a support phone service and a community forum.

The Rare Cancer Alliance offer support and information to people affected by rare cancers.

Last reviewed: 
01 Dec 2020
Next review due: 
01 Dec 2023
  • Acute myeloblastic leukaemias in adult patients: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up

    M Fey and others

    Annals of Oncology, 2013. Volume 24, supplement 6, pages vi138-vi143

  • arsenic trioxide (Trisenox)

    Scottish Medicines Compendium, July 2019

  • Acute Promyelocytic Leukemia (APL, APML)

    SR Cingam and NV Koshy

    StatPearls Publishing LLC, 2019

  • Arsenic trioxide for treating acute promyelocytic leukaemia

    National Institute for Health and Care Excellence (NICE), 2018

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