From the Guidelines
Monocytosis is a clinically significant finding that may indicate an underlying hematological malignancy, such as chronic myelomonocytic leukemia (CMML).
Diagnostic Criteria
The diagnosis of CMML is based on comprehensive diagnostic criteria, including:
- Persistent peripheral blood monocytosis (> 1×10^9/L)
- No Philadelphia chromosome or BCR-ABL1 fusion gene
- No arrangement of PDGFRA or PDGFRB
- Less than 20% blasts in the peripheral blood and the bone marrow
- At least one of the following: dysplasia in one or more cell lines, an acquired clonal cytogenetic abnormality or molecular genetic abnormality present in hematopoietic cells, or persistence of monocytosis for at least 3 months and no evidence of other causes of monocytosis 1.
Clinical Significance
Monocytosis can be a sign of an underlying condition that requires prompt evaluation and treatment. In the context of CMML, monocytosis is a key diagnostic criterion, and its presence can help guide treatment decisions. The WHO classification provides a framework for diagnosing and managing CMML, including the evaluation of patients at diagnosis, prognosis and risk classification, and determinants of therapeutic interventions 1.
Key Points
- Monocytosis is a significant finding that requires further evaluation to rule out underlying hematological malignancies
- CMML is a type of leukemia that is characterized by persistent peripheral blood monocytosis and other diagnostic criteria
- The WHO classification provides a framework for diagnosing and managing CMML, including the evaluation of patients at diagnosis and treatment decisions 1.
From the Research
Clinical Significance of Monocytosis
The clinical significance of monocytosis can be understood by examining its relationship with various diseases and conditions.
- Monocytosis has been observed in patients with infections, cardiovascular and inflammatory diseases, cancer, and autoimmune diseases 2.
- In patients with adult T-cell leukaemia/lymphoma, monocytosis is associated with a poorer prognosis 3.
- Monocytosis can be an indicator of various inflammatory diseases, and inflammatory monocyte subsets are valuable biomarkers for inflammatory diseases, including cardiovascular diseases 4.
- Clonal monocytosis can lead to kidney abnormalities, including acute kidney injury and chronic kidney disease, and is a predictor of worse outcomes in patients with chronic myelomonocytic leukemia 5.
- In polycythemia vera, monocytosis is associated with older age, higher frequencies of leukocytosis, and TET2/SRSF2 mutations, and may adversely affect overall and myelofibrosis-free survival 6.
Prognostic Factors
Monocytosis can be a prognostic factor in various diseases, including:
- Adult T-cell leukaemia/lymphoma, where absolute monocyte counts above 1.5 x 10(9)/l are associated with a poorer prognosis 3.
- Polycythemia vera, where an absolute monocyte count of ≥1.5 × 10^9 /L may adversely affect overall and myelofibrosis-free survival 6.
- Chronic myelomonocytic leukemia, where clonal monocytosis is a predictor of worse outcomes 5.
Biomarkers
Inflammatory monocyte subsets are valuable biomarkers for inflammatory diseases, including: