Different Types of Myelodysplastic Syndromes

There are many types of MDS and this can be difficult to understand. Spend time talking to your doctor or nurse about this. It’s important that you know and understand your exact diagnosis.

There is a generally accepted classification system for separating the different types of Myelodysplastic Syndromes. This system is based on the blood results, the appearance of the bone marrow and any chromosome changes found.

The World Health Organization (WHO) regularly updates this classification based on how the bone marrow looks and the number of leukaemia cells seen. These leukaemia cells are called blasts, which may be increased in some of the types of MDS.

There are six broad types of MDS included in the current classification (2008):

  • Refractory cytopenia with unilineage dysplasia (RCUD)
  • Refractory anaemia with ring sideroblasts (RARS)
  • Refractory cytopenia with multilineage dysplasia (RCMD)
  • Refractory anaemia with excess blasts (RAEB)
  • Myelodysplastic syndrome unclassified (MDS-U)
  • MDS associated with del(5q), including the 5q- syndrome

Low blood counts are called 'cytopenias'.

'Dysplasia' means that the bone marrow cells look abnormal.

'Sideroblasts' are young red cells that typically have a ring of iron granules when seen under the microscope.

Del(5q) is a specific type of MDS where chromosome tests show part of the chromosome five is missing.

'Refractory' means obstinate, and refers to the fact that the low blood count seems resistant to treatment.

Understanding Myelodysplastic Syndromes

This booklet has been written to help you understand more about MDS. Learn more about the different types of MDS  in Chapter 5.

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Chronic Myelomonocytic Leukaemia

In the past, Chronic myelomonocytic leukaemia (CMML) was considered a type of MDS. In CMML, one specific type of white cell is raised in the blood.  Bloodwise provides a CMML Factsheet. Other booklets from Bloodwise with loads of useful information are available on their download page: Patient information booklets.

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Video: Chronic Myelomonocytic Leukaemia

This presentation is very scientific, but stresses the importance of knowing your exact gene mutations.
Treatments such as Azacitidine are mentioned to be of benefit, but clearly much more needs to be done for patients with this specific type of MDS/MPN overlap disease.
This is also the reason why it is crucial to be seen at a specialist center for MDS if you have been diagnosed with CMML

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