[2] For a diagnosis of CMML, the World Health Organization (WHO) states that the blood monocyte count must be >1x109/L, no Philadelphia chromosome or mutations in the PDGFRA or PDGFRB gene should be present, the blast count must be <20% and dysplasia of at least one lineage of myeloid blood cell should be present.

[10] With a high rate of Ras mutation in CMML, deregulation of this signalling pathway has been linked to the pathogenesis of the disease.

This disease is associated with a highly variable set of disorders including the myelodysplastic syndrome, acute myeloid leukemia, and CMML.

Other features may include; leukocytosis (50% of cases); left shift and dysplasia of monocytes and granulocytes; presence of metamyelocytes, myelocytes and promonocytes; monocytes with hypersegmented/abnormal shaped nuclei, increased cytoplasmic basophilia and/or the presence of cytoplasmic granules; eosinophilia (in cases of CMML with eosinophilia); and spherocytosis (in cases of direct Coombs test, DCT, positive haemolytic anaemia).

[7][9] Bone marrow aspirates will display hypercellularity with increased counts of granulocytic and monocytic cells.

[1] Bone marrow core biopsies may show a predominance of myelocytic and monocytic cells, abnormal localisation of immature precursors and dysplastic megakaryocytes.

[17] Leukemia subtypes are categorised into single clinical entities so that they can be diagnosed and treated appropriately.

Leukaemias are subdivided into lymphoid and myeloid neoplasms, depending on which bone marrow cells are cancerous.

Other diseases in this category are juvenile myelomonocytic leukaemia, atypical CML; BCR-ABL1 negative and MDS/MPD unclassifiable.

The 2008 revision of the classification moved cases of CMML with PDGFR gene translocations to a new group, myeloid/lymphoid neoplasms with eosinophilia with abnormalities of PDGFRA, PDGFRB or FGFR1.

[8] Presence of two or more phenotypic abnormalities can aid a diagnosis of CMML in the absence of identifying cytogenetic or dysplastic features.

Trisomy 8, chromosome 7 abnormalities and complex karyotypes comprise a high risk group.

[12][22][23] The International Prognostic Scoring System (IPSS) was developed in the mid-1990s to assess the prognosis of MDS patients.

It uses the blast percentage, number of cytopenias and bone marrow cytogenetics data to place cases of CMML into these groups.

Anderson Cancer Center found that a haemoglobin level of <12g/dL, total circulating lymphocyte count of >2.5 x 109/L, >0% immature myeloid cells, >10% bone marrow blasts causes a reduced overall survival.

[25][26] The Düsseldorf score stratifies cases using four categories, giving one point for each; bone marrow blasts ≥5%, LDH >200U/L, haemoglobin ≤9g/dL and a platelet count ≤100,000/uL.

Indications for treatment include the presence of B symptoms, symptomatic organ involvement, increasing blood counts, hyperleukocytosis, leukostasis and/or worsening cytopenias.

[6][10] Blood transfusions and erythropoietin administration are used to raise haemoglobin levels in cases with anemia.

Decitabine is a similar drug to azacitidine and is approved by the FDA for treatments of all subtypes of MDS, including CMML.

[4][10][12] Decitabine/cedazuridine (Inqovi) is a fixed-dosed combination medication for the treatment of adults with myelodysplastic syndromes (MDS) and chronic myelomonocytic leukemia (CMML) that was approved for use in the United States in July 2020.