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The diverse functions of monocytes in humans. Monocytes are characterized by expression of several cell surface receptors. This figure highlights some of those receptors and the key monocyte-associated functions such as macrophage-associated phagocytosis, dendritic cell-mediated antigen presentation, wound healing, interactions with coagulation cascade, and regulation of inflammatory responses (created with BioRender.com)
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Purpose of Review
Monocytosis is a frequently encountered clinical condition that needs appropriate investigation due to a broad range of differential diagnoses. This review is meant to summarize the latest literature in the diagnostic testing and interpretation and offer a stepwise diagnostic approach for a patient presenting with monocytosis.
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... Broadly, monocytosis can be grouped into two primary categories based on its causes: -Reactive monocytosis: This form arises as a response to various conditions such as acute infections, post-splenectomy status, chronic infections and rheumatologic diseases. -Clonal monocytosis: This is associated with hematologic malignancies and disorders like acute monocytic or myelomonocytic leukemia, chronic myelomonocytic leukemia, juvenile myelomonocytic leukemia, essential thrombocythemia, polycythemia vera and primary myelofibrosis [82]. ...
Cardiovascular disease, particularly coronary artery disease (CAD), remains a predominant cause of mortality globally. Factors such as atherosclerosis and inflammation play significant roles in the pathogenesis of CAD. The nexus between inflammation and CAD is underscored by the role of immune cells, such as neutrophils, lymphocytes, monocytes, and macrophages. These cells orchestrate the inflammatory process, a core component in the initiation and progression of atherosclerosis. The activation of these pathways and the subsequent lipid, fibrous element, and calcification accumulation can result in vessel narrowing. Hematological parameters derived from routine blood tests offer insights into the underlying inflammatory state. Recent studies have highlighted the potential of inflammatory hematological ratios, such as the neutrophil/lymphocyte ratio, platelet/lymphocyte ratio, monocyte/lymphocyte ratio and lymphocyte/monocyte ratio. These parameters are not only accessible and cost-effective but also mirror the degree of systemic inflammation. Several studies have indicated a correlation between these markers and the severity, prognosis, and presence of CAD. Despite the burgeoning interest in the relationship between inflammatory markers and CAD, there remains a paucity of data exploring these parameters in young patients with acute myocardial infarction. Such data could offer valuable insights into the unique pathophysiology of early-onset CAD and improve risk assessment and predictive strategies.
... Ground-glass opacification has been shown to be associated with sarcoid granulomas [21]. The occurrence of eosinophilia and monocytosis can indicate the presence of a chronic inflammatory process of various aetiologies such as infectious causes, e.g., tuberculosis [22]. However, in the present case, both the eosinophil and monocyte count lie within the normal range. ...
Background
Necrotising granulomatous diseases of the lungs exhibit a narrow range of differential diagnoses. Tuberculosis accounts for most of these cases, while sarcoidosis is an uncommon entity in this group but both possess similar clinical and radiological similarities. One must consider a diagnosis of sarcoidosis once the standard anti-mycobacterial medications fail to achieve a clinical improvement. The case described highlights the coexistence of tuberculosis and sarcoidosis which is a rare entity in the medical literature.
Case presentation
A 57-year-old male presented with respiratory symptoms and was diagnosed with tuberculosis (TB) demonstrating a polymerase chain reaction (PCR) test positive showing microbial DNA in bronchial washing. The patient started standard anti-TB treatment; however, he did not respond initially. Further investigations led us to diagnose pulmonary followed by skin sarcoidosis, based on histology. After confirmation of sarcoidosis, administered corticosteroids for 6 months simultaneously along with anti-TB treatment; however, anti-TB treatment was prolonged for a total of 9 months. The patient was found clinically symptomless after the completion of treatment during subsequent follow-ups.
Conclusion
The use of corticosteroids as an adjunct with standard anti-TB treatment proves beneficial effects on the recovery of patients having a coexistence of pulmonary mycobacterium tuberculosis and sarcoidosis disease conditions.
... It is known that monocytosis can be caused by a wide variety of neoplastic and nonneoplastic conditions [33]. The various causes of monocytosis can be divided into two broad categories: clonal or reactive, from which acute infections such as endocarditis can be an etiologic factor [34]. Infective-endocarditis-related bacteria are described in the literature as activating factors of blood monocytes. ...
Background
Over the last two decades, several cases of infections caused by Lactococcus lactis have been reported. This Gram-positive coccus is considered non-pathogenic for humans. However, in some rare cases, it can cause serious infections such as endocarditis, peritonitis, and intra-abdominal infections.
Case presentation
A 56-year-old Moroccan patient was admitted to the hospital because of diffuse abdominal pain and fever. The patient had no past medical history. Five days before his admission, he developed abdominal pain in the right lower quadrant along with chills and feverish sensations. Investigations showed a liver abscess, which was drained, and the microbiological study of the pus revealed Lactococcus lactis subsp. cremoris. Three days after admission, control computed tomography objectified splenic infarctions. Cardiac explorations were performed and showed a floating vegetation on the ventricle side of the aortic valve. We retained the diagnosis of infectious endocarditis according to the modified Duke criteria. The patient was declared afebrile on day 5 and the evolution was clinically and biologically favorable. Lactococcus lactis subsp. cremoris, formerly known as Streptococcuscremoris, is a rare cause of human infections. The first case of Lactococcus lactiscremoris endocarditis was reported in 1955. This organism includes three subspecies: lactis, cremoris, and hordniae. A MEDLINE and Scopus search showed only 13 cases of infectious endocarditis due to Lactococcus lactis, with subsp. cremoris identified in four of the cases.
Conclusions
To our knowledge, this is the first case report of the co-occurrence of Lactococcus lactis endocarditis and liver abscess. Despite its reported low virulence and good response to antibiotic treatment, Lactococcus lactis endocarditis must be considered a serious disease. It is imperative for a clinician to suspect this microorganism of causing endocarditis when they notice signs of infectious endocarditis in a patient with a history of consumption of unpasteurized dairy products or contact with farm animals. The finding of a liver abscess should lead to an investigation of endocarditis, even in previously healthy patients without obvious clinical signs of endocarditis.
... [2,3] Monocytosis in hospital settings is usually secondary (or reactive) due to nonneoplastic causes such as chronic infections, systemic inflammatory disorders, autoimmune diseases, and drug reactions. [4] Hence, a large number of slides have to be screened to rule out hematological malignancies (HD) associated with monocytosis. One of the most important neoplastic differentials is chronic myelomonocytic leukemia (CMML) which is classified under myelodysplastic/ myeloproliferative neoplasm in the WHO 2016 as well as 2022. ...
... These findings highlight the gender disparity observed in DM which could be, at least in part, explained by sex-specific monocyte physiology and differential sex steroid availability and its influence on insulin sensitivity and glucose homeostasis [12,30]. ...
... The requirement of these factors for the observed association between MLR and FBG must be established in future studies. These findings highlight the gender disparity observed in DM which could be, at least in part, explained by sex-specific monocyte physiology and differential sex steroid availability and its influence on insulin sensitivity and glucose homeostasis [12,30]. Figure 2E,F, respectively. ...
Background:
Abnormalities in fasting blood glucose (FBG) resulting in hypoglycemia (OG), impaired fasting glycemia (IFG), or hyperglycemia (HG) arise from disordered metabolic regulation caused in part by inflammation. To date, there is a dearth of evidence regarding the clinical utility of the monocyte-lymphocyte ratio (MLR), an emerging inflammatory index, in the management of dysglycemia.
Methods:
This retrospective, cross-sectional study explored MLR fluctuations as a function of glycemic control in 14,173 Saudi subjects. Data collected from 11 August 2014 to 18 July 2020 were retrieved from Al-Borg Medical Laboratories. Medians were compared by Mann-Whitney U or Kruskal-Wallis tests and the prevalence, relative risk (RR), and odds ratio (OR) were calculated.
Results:
MLR was significantly elevated in IFG (p < 0.0001) and HG (p < 0.05) groups compared to the normoglycemia (NG) group, and individuals with elevated MLR (>0.191) had significantly increased FBG (p < 0.001). The risk of IFG (RR = 1.12, 95% CI: 1.06-1.19, p < 0.0002) and HG (RR = 1.10, 95% CI: 1.01-1.20, p < 0.0216) was significantly increased if MLR was elevated, and individuals with elevated MLR were 1.17 times more likely to have IFG (OR = 1.17, 95% CI: 1.08-1.26, p < 0.0002) and 1.13 times more likely to have HG (OR = 1.13, 95% CI: 1.02-1.24, p < 0.0216).
Conclusion:
Elevated MLR is correlated with and carries a greater risk for IFG and HG. However, large prospective cohort studies are needed to establish the temporal relationship between MLR and FBG and to examine the prognostic value of this novel marker.
... 30 The transient increase of monocytes observed during the first 3 days p.i. reflects the classical response to inflammation caused by the intravenous injection of the viral vector. 52 MVA is also known to activate and induce proliferation of NK cells in mice and NHP. 53,54 In addition, IL-7 may also contribute to the maturation and the survival of NK cells. ...
Persistence of an immunosuppression, affecting both the innate and adaptive arms of the immune system, plays a role in sepsis patients’ morbidity and late mortality pointing to the need for broad and effective immune interventions. MVA-hIL-7-Fc is a non-replicative recombinant Modified Vaccinia virus Ankara encoding the human interleukin-7 fused to human IgG2 Fc fragment. We have shown in murine sepsis models the capacity of this new virotherapy to stimulate both arms of the immune system and increase survival. Herein, an exploratory study in nonhuman primates was performed following a single intravenous injection of the MVA-hIL-7-Fc used at the clinical dose to assess its safety and biological activities. Four cynomolgus macaques were followed for 3 weeks post-injection (p.i), without observed acute adverse reactions. Circulating hIL-7-Fc was detected during the first 3–5 days p.i with a detection peaking at 12 h p.i. IL-7 receptor engagement and downstream signal transduction were detected in T cells demonstrating functionality of the expressed IL-7. Expansion of blood lymphocytes, mainly CD4 and CD8 naïve and central memory T cells, was observed on day 7 p.i. together with a transient increase of Ki67 expression on T lymphocytes. In addition, we observed an increase in circulating B and NK cells as well as monocytes were albeit with different kinetics and levels. This study indicates that a vectorized IL-7-Fc, injected by intravenous route at a relevant clinical dose in a large animal model, is active without adverse reactions supporting the clinical development of this novel virotherapy for treatment of sepsis patients.
... As to the unusual coexistence of driver gene mutations, a JAK2/CALR double-mutated genotype has been reported rarely in MPNs and does not correlate with specific clinical phenotypes [49,52]. Finally, it should be stressed that monocytosis in MPNs is mostly observed alongside fibrotic progression and may be assumed as an indicator of accelerated phase disease [53,54]. This was not the case for our patient. ...
Myeloproliferative neoplasms (MPNs) are a heterogeneous group of clonal hematopoietic stem cell disorders, characterized by increased proliferation of one or more myeloid lineages in the bone marrow. The classification and diagnostic criteria of MPNs have undergone relevant changes over the years, reflecting the increased awareness on these conditions and a better understanding of their biological and clinical-pathological features. The current World Health Organization (WHO) Classification acknowledges four main sub-groups of MPNs: (i) Chronic Myeloid Leukemia; (ii) classical Philadelphia-negative MPNs (Polycythemia Vera; Essential Thrombocythemia; Primary Myelofibrosis); (iii) non-classical Philadelphia-negative MPNs (Chronic Neutrophilic Leukemia; Chronic Eosinophilic Leukemia); and (iv) MPNs, unclassifiable (MPN-U). The latter are currently defined as MPNs with clinical-pathological findings not fulfilling the diagnostic criteria for any other entity. The MPN-U spectrum traditionally encompasses early phase MPNs, terminal (i.e., advanced fibrotic) MPNs, and cases associated with inflammatory or neoplastic disorders that obscure the clinical-histological picture. Several lines of evidence and clinical practice suggest the existence of additional myeloid neoplasms that may expand the spectrum of MPN-U. To gain insight into such disorders, this review addresses the history of MPN classification, the evolution of their diagnostic criteria and the complex clinical-pathological and biological features of MPN-U.
We aimed to examine the association between relative monocytosis and the recurrence of pulmonary Langerhans Cell Histiocytosis. Clinical, laboratory, radiographic and treatment data for 86 patients with a histopathological diagnosis of Langerhans Cell Histiocytosis over a 20-year duration. Parameters such as biological sex, age at diagnosis, time to diagnosis, molecular diagnostic data and imaging were collected. Treatment responses were assessed predominantly through radiography, with RECIST 1.1 criteria applied to MRI or CT scans and PERCIST utilized for serial PET imaging. Investigators also assessed peripheral blood absolute monocyte count at various time points, including initial diagnosis and the most recently available value. While peripheral blood absolute monocyte count between the earliest assessed timepoint and latest value did not differ, the mean value on progression (0.94 K/µL), however, was significantly higher than that following re-institution of therapy (0.31, p = 0.000794. Our observation of relative monocytosis on LCH disease progression may be related to an increase in circulating LCH on disease progression or from increased monocyte production for later differentiation into mature dendritic cells that participate in MHC Class 1 upregulation. This trend is especially evident in pulmonary LCH which is incited by tissue trauma and irritation by environmental factors. The phenomena observed in our study parallel other non-LCH cohorts, specifically in published findings from our own group in patients with Rosai Dorfman and Erdheim Chester Disease. To further elucidate the molecular underpinnings of LCH and explore the etiology of this monocyte trend, expanded integrated genomic-transcriptomic sequencing analyses to evaluate the molecular character of LCH and ultimately clarify the origin of this monocyte trend are in progress. These studies are poised to offer invaluable insight to the molecular mechanisms underlying LCH, specifically as they pertain to monocyte signaling and differentiation.
