From the Guidelines
Elevation of monocytes is primarily caused by chronic infections, inflammatory conditions, and certain malignancies, with the most recent evidence suggesting that stress responses, such as those experienced by athletes, can also lead to increased monocyte levels 1.
Causes of Monocytosis
The causes of monocytosis can be broadly categorized into:
- Chronic infections, such as tuberculosis, bacterial endocarditis, fungal infections, and viral illnesses like mononucleosis
- Inflammatory disorders, such as inflammatory bowel disease, rheumatoid arthritis, and systemic lupus erythematosus
- Hematologic malignancies, particularly chronic myelomonocytic leukemia and monocytic leukemia
- Other causes, including recovery from bone marrow suppression, certain medications (corticosteroids, carbamazepine), stress responses, and autoimmune neutropenia
Diagnostic Criteria
According to the study by Haematologica 1, the diagnostic criteria for chronic myelomonocytic leukemia include:
- 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, or persistence of monocytosis for at least 3 months and no evidence of other causes of monocytosis
Recent Evidence
A recent study published in Sports Medicine 1 found that monocytes increase after different types of exercise and return to baseline levels within 2 hours post-exercise. This suggests that stress responses, such as those experienced by athletes, can also lead to increased monocyte levels.
Conclusion is not allowed, so the answer will be ended here.
From the Research
Elevation of Monocytes
- The provided studies do not directly address the causes of elevation of monocytes 2, 3, 4, 5, 6.
- However, some studies mention the effects of certain treatments on blood cell counts, such as neutropenia and leucocytopenia, which can be related to monocyte counts 3, 4.
- For example, a study on rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisolone in patients with newly diagnosed diffuse large B-cell non-Hodgkin lymphoma mentions that grade 3 or 4 neutropenia was higher in the R-CHOP-21 group 3.
- Another study on intravascular large B-cell lymphoma treated with R-CHOP combined with high-dose methotrexate plus intrathecal chemotherapy reports that the most frequent adverse events of grade 3-4 were neutropenia and leucocytopenia 4.
- However, these studies do not specifically investigate the causes of elevated monocytes, and more research would be needed to determine the relationship between these treatments and monocyte counts.
Related Conditions and Treatments
- Some studies discuss the management of patients with latent tuberculosis infection requiring biologic therapy in rheumatology and dermatology clinical practice, which may involve the use of corticosteroids and disease-modifying anti-rheumatic drugs that could potentially affect monocyte counts 5.
- Another study examines the outcomes of methotrexate-associated lymphoproliferative disorders in rheumatoid arthritis patients treated with disease-modifying anti-rheumatic drugs, which could also be related to monocyte counts 6.
- However, these studies do not provide direct evidence on the causes of elevation of monocytes.