From the Guidelines
Monocytosis is defined as a persistent peripheral blood monocytosis with a count of more than 1×10^9/L.
Diagnostic Criteria
The definition of monocytosis is based on the comprehensive diagnostic criteria proposed by the WHO classification in 2001, which includes:
- Persistent peripheral blood monocytosis (> 1×10^9/L) 1
- 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, or persistence of monocytosis for at least 3 months with no evidence of other causes
Key Points
- The monocytosis count is a critical factor in the diagnosis of chronic myelomonocytic leukemia (CMML) 1
- The WHO classification provides a clear definition of monocytosis, which is essential for accurate diagnosis and treatment 1
From the Research
Definition of Monocytosis
- Monocytosis is defined as an increase in the number of monocytes in the blood, with a threshold value of 0.8×10⁹ cells/L 2.
- It is a common finding that can be caused by a wide variety of neoplastic and non-neoplastic conditions, including infections, rheumatic disorders, and myeloproliferative disorders 3, 2.
- Monocytosis can be associated with chronic infections, such as tuberculosis or endocarditis, as well as cardiovascular diseases, including atherosclerosis and coronary artery disease 2, 4.
Characteristics of Monocytosis
- Monocytes are part of the vertebrate innate immune system and are produced by bone marrow and splenic progenitors that derive from hematopoietic stem cells (HSCs) 4.
- Monocytosis can be characterized by the presence of immature monocytes, promonocytes, or monoblasts in the peripheral blood or bone marrow 3, 5.
- The diagnosis of monocytosis requires confirmation by reading under a microscope by an experienced biologist, as well as the integration of laboratory data, morphology, clinical findings, and ancillary studies 3, 6.
Clinical Significance of Monocytosis
- Monocytosis can predict adverse outcomes in patients admitted to the emergency department, including increased 30-day mortality and length of stay 2.
- The presence of monocytosis can be influenced by various factors, including age, gender, comorbidities, and main diagnosis 2.
- Understanding monocytosis and its consequences in disease can reveal new therapeutic opportunities without compromising steady-state functions 4.