Chronic myelomonocytic leukemia

Definition

• FAB: Essentially, MDS with overproduction of monocytes
• WHO: Monocyte count >1x10^9^, 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

Epidemiology

• Median age at diagnosis: 65-75

Clinical Manifestations

• Splenomegaly (common)
• Anaemia, fever, night sweats, weight loss, infection, bleeding, synovitis, lymphadenopathy, skin rashes, pleural effusion, pericardial effusion and peritoneal effusion

Diagnosis

• FAB
  • Monocyte count >1x109/L
  • <20% blasts in bone marrow
  • <5% blasts in peripheral blood
• WHO
  • Persistent peripheral blood monocytosis with counts >1x10^9^/L
  • No Philadelphia chromosome or BCR-ABL1 fusion gene
  • No rearrangement of PDGFRA or PDGFRB gene
  • <20% myeloblasts, monoblasts and promonocytes in peripheral blood or bone marrow
  • Dysplasia in one or more of the myeloid lineages; if myelodysplasia is absent or minimal then a diagnosis of CMML can be made if other requirements are met and:
    • A molecular genetic abnormality is present in haematopoietic cells, or
    • Monocytosis present for ≥3 months and other causes of monocytosis have been ruled out