From the Guidelines
Elevated monocytes, or monocytosis, is a condition that warrants further investigation due to its potential association with underlying infections, inflammation, or diseases, and management should focus on addressing the underlying cause rather than the elevated monocytes themselves. When evaluating a patient with elevated monocytes, it is essential to consider the comprehensive diagnostic criteria, including persistent peripheral blood monocytosis (> 1×10^9/L), no Philadelphia chromosome or BCR-ABL1 fusion gene, and less than 20% blasts in the peripheral blood and bone marrow 1. Some key points to consider in the evaluation and management of elevated monocytes include:
- Persistent peripheral blood monocytosis (> 1×10^9/L) as a key diagnostic criterion 1
- The importance of ruling out other causes of monocytosis, such as infection, inflammation, or malignancy 1
- The need for a thorough evaluation, including additional blood tests, physical examination, and review of medical history
- Management focusing on addressing the underlying cause, rather than the elevated monocytes themselves
- The potential for elevated monocytes to be associated with certain diseases, such as chronic myelomonocytic leukemia (CMML), and the importance of considering this in the diagnostic workup 1. It is crucial to consult with a healthcare provider for a thorough evaluation and to determine the best course of management, as treatment will vary greatly depending on the identified cause.
From the Research
Implications of Elevated Monocytes
Elevated monocytes have been associated with various pathological conditions, including:
- Infections, such as hepatitis B, hepatitis C, amebiasis, leishmaniasis, schistosomiasis, or echinococcosis 2
- Cardiovascular diseases, where monocytes play a crucial role in vascular injury repair and are involved in the development of atherosclerosis 3
- Inflammatory diseases, such as autoimmune diseases, where monocytes accumulate and play an inflammatory and tissue destructive role 4
- Cancer, where monocytes can be used as diagnostic and therapeutic targets 3
Monocyte Subsets and Their Role in Disease
Monocytes can be divided into three subsets: classical, intermediate, and non-classical, each playing a specific role in the control, development, and escalation of immunological processes 5.
- Intermediate monocytes have been associated with type 1 diabetes susceptibility and progression, and their ratio to nonclassical monocytes correlates with the decline in functional β cell mass 6
- NK-like monocytes, characterized by the expression of CD14, CD16, HLA-DR, KLRD1, and PRF1, are elevated in patients with recent onset type 1 diabetes and correlate with clinical progression 6
Monocyte Dysfunction and Disease Consequences
Monocyte dysregulation can lead to consequences such as:
- Maintaining inflammation and supporting resolution of inflammation in infectious and non-infectious liver diseases 2
- Inhibiting T cell proliferation and limiting the T cell response to autoantigens in target tissues, which can lead to clinical improvement in autoimmune diseases 4
- Contributing to the development of cardiovascular diseases, where monocytes play a crucial role in vascular injury repair 3