From the Guidelines
Monocytosis is primarily caused by infections, inflammatory conditions, and certain malignancies, with bacterial infections, chronic inflammatory disorders, and hematologic malignancies being significant causes, as supported by studies such as 1 and 1.
Causes of Monocytosis
The causes of monocytosis can be broadly categorized into:
- Infections: Bacterial infections like tuberculosis, endocarditis, and typhoid fever, as well as fungal and protozoal infections, can trigger monocytosis.
- Inflammatory conditions: Chronic inflammatory disorders such as inflammatory bowel disease, rheumatoid arthritis, and sarcoidosis can lead to elevated monocyte counts.
- Malignancies: Hematologic malignancies, particularly chronic myelomonocytic leukemia, acute monocytic leukemia, and Hodgkin lymphoma, are significant causes of monocytosis.
- Other causes: Recovery from bone marrow suppression, certain medications (corticosteroids, carbamazepine), and autoimmune disorders may also result in monocytosis, as noted in studies like 1.
Diagnostic Considerations
The diagnostic workup for suspected chronic myelomonocytic leukemia (CMML) should include patient history, physical examination, complete blood count, peripheral blood smear examination, bone marrow aspiration and biopsy, and molecular assays to exclude certain genetic abnormalities, as recommended in 1 and 1.
Clinical Significance
A monocyte count above 800/μL in adults typically indicates monocytosis, though the clinical significance depends on the underlying cause rather than the absolute number, highlighting the importance of considering the broader clinical context, as discussed in 1 and 1.
From the Research
Causes of Monocytosis
- Monocytosis is a common finding that is caused by a wide variety of neoplastic and non-neoplastic conditions 2
- The condition can be caused by various factors, including chronic myelomonocytic leukemia, a prototypical neoplasm with monocytosis, which can be distinguished from other reactive or neoplastic causes through flow cytometry studies 3
Diagnostic Approach
- A stepwise diagnostic approach is recommended for patients presenting with monocytosis, involving the integration of laboratory data, morphology, clinical findings, and ancillary studies 2, 3
- An algorithmic approach to the diagnosis of monocytosis can help clinicians distinguish between different etiologies and provide a reference guide for diagnosis 3