Canterbury DHB



It is important to distinguish reactive causes of cytopenias and dysplasia from primary bone marrow dysfunction i.e. myelodysplasia. This begins with a good clinical history specifically looking for previous exposure to chemotherapy, radiotherapy, immunotherapy, and occupational or other exposure to potential causative agents e.g. benzenes. A full medical, medication, and social history is required because the majority of patients with MDS are elderly. Specific follow-up investigations are dictated by the history.

The blood film and a bone marrow examination are the important investigations to establish a diagnosis (see the WHO classification for specific criteria). Cytogenetics should be tested in all cases because this forms an important part of the prognostic scoring system. The gold standard is a composite report which includes blood film, bone marrow aspirate and trephine, flow cytometry, and genetic testing.

Bone marrow aspirate

Standard MGG or Wrights stain and iron stain. If the sample is aparticulate, it may not be possible to make the diagnosis based on the aspirate alone.

Bone marrow trephine

Standard H+E and reticulin stain.


Flow cytometry


Genotype-phenotype correlation


Ogawa S. Genetics of MDS. Blood 2019 133; 10: 1049

Summary of the WHO Categories of Myelodysplasia

Summary of the WHO Categories of Myelodysplastic/Myeloproliferative Diseases

See WHO classification (2016): Table 11. Diagnostic criteria for CMML (page 8)


CMML is a disorder with features of both myeloproliferation and myelodysplasia. The median age at presentation is 76 years and it is associated with a short median survival of 20 months (range 7-60). The aggressive nature of the disease and the fact that most patients are older with comorbidities mean that it is difficult to treat.

A proportion of patients have more indolent disease with a low level peripheral blood monocytosis which simply needs to be monitored.

Indications for treatment:

Treatment options include:

Allogeneic stem cell transplantation is only available to a limited number of patients with CMML but should be considered in younger patients and those with poor risk disease who have a low comorbidity index. Patients may require intensive AML-type chemotherapy prior to proceeding with transplantation.

CMML can be divided into a proliferative type, generally WBC >13 x 109/L and a dysplastic type, WBC <13 x 109/L. In general the proliferative type has a worse outcome. The percentage of blasts also has a clear prognostic significance and it is important that the promonocytes are counted as blasts and separated from the mature monocytes in the cell differential. Perform flow cytometry because it helps distinguish the cell types.

Sub-types of CMML


% blasts in peripheral blood

% blasts in bone marrow










+ If Auer rods are present in the blasts, classification is CMML-2.

Diagnostic criteria for the other main subtypes of MDS/MPN can be found in the following links. This includes atypical CML (aCML), MDS/MPN with ring sideroblasts and thrombocytosis and juvenile myelomonocytic leukaemia. The SETBP1 mutation can be found in up to one third of cases of aCML.

Atypical CML

This is a challenging disorder to diagnose and treat due to its presentation in older adults and aggressive course with high rates of transformation to AML. The following article provides a good summary of treatment options.

Gotlib, J. (2017). "How I treat atypical chronic myeloid leukemia." Blood 129(7): 838-845.

MDS/MPN with ringed sideroblasts and thrombocytosis

A new entity in the 2016 WHO classification of MDS/MPN which replaces "Refractory anaemia with ringed sideroblasts and thrombocytosis".



About this Canterbury DHB document (4953):

Document Owner:

Emma-Jane McDonald (see Who's Who)

Last Reviewed:

November 2019

Next Review:

November 2021


Note: Only the electronic version is controlled. Once printed, this is no longer a controlled document. Disclaimer

Topic Code: 4953