Droplet digital PCR: An effective method for monitoring and prognostic evaluation of minimal residual disease in JMML.

Juvenile myelomonocytic leukaemia (JMML) is a rare myeloproliferative neoplasm requiring haematopoietic stem cell transplantation (HSCT) for potential cure. Relapse poses a significant obstacle to JMML HSCT treatment, as the lack of effective minimal residual disease (MRD)-monitoring methods leads to delayed interventions. This retrospective study utilized the droplet digital PCR (ddPCR) technique, a highly sensitive nucleic acid detection and quantification technique, to monitor MRD in 32 JMML patients. The results demonstrated that ddPCR detected relapse manifestations earlier than traditional methods and uncovered molecular insights into JMML MRD dynamics. The findings emphasized a critical 1- to 3-month window post-HSCT for detecting molecular relapse, with 66.7% (8/12) of relapses occurring within this period. Slow MRD clearance post-HSCT was observed, as 65% (13/20) of non-relapse patients took over 6 months to achieve ddPCR-MRD negativity. Furthermore, bone marrow ddPCR-MRD levels at 1-month post-HSCT proved to be prognostically significant. Relapsed patients exhibited significantly elevated ddPCR-MRD levels at this time point (p = 0.026), with a cut-off of 0.465% effectively stratifying overall survival (p = 0.007), event-free survival (p = 0.035) and cumulative incidence of relapse (p = 0.035). In conclusion, this study underscored ddPCR's superiority in JMML MRD monitoring post-HSCT. It provided valuable insights into JMML MRD dynamics, offering guidance for the effective management of JMML.

Biallelic inactivation of the NF1 tumour suppressor gene in juvenile myelomonocytic leukaemia: Genetic evidence of driver function and implications for diagnostic workup.

Juvenile myelomonocytic leukaemia (JMML) is characterized by gene variants that deregulate the RAS signalling pathway. Children with neurofibromatosis type 1 (NF-1) carry a defective NF1 allele in the germline and are predisposed to JMML, which presumably requires somatic inactivation of the NF1 wild-type allele. Here we examined the two-hit concept in leukaemic cells of 25 patients with JMML and NF-1. Ten patients with JMML/NF-1 exhibited a NF1 loss-of-function variant in combination with uniparental disomy of the 17q arm. Five had NF1 microdeletions combined with a pathogenic NF1 variant and nine carried two compound-heterozygous NF1 variants. We also examined 16 patients without clinical signs of NF-1 and no variation in the JMML-associated driver genes PTPN11, KRAS, NRAS or CBL (JMML-5neg) and identified eight patients with NF1 variants. Three patients had microdeletions combined with hemizygous NF1 variants, three had compound-heterozygous NF1 variants and two had heterozygous NF1 variants. In addition, we found a high incidence of secondary ASXL1 and/or SETBP1 variants in both groups. We conclude that the clinical diagnosis of JMML/NF-1 reliably indicates a NF1-driven JMML subtype, and that careful NF1 analysis should be included in the genetic workup of JMML even in the absence of clinical evidence of NF-1.

Role of allogeneic transplantation in chronic myelomonocytic leukemia: an international collaborative analysis.

To determine the survival benefit of allogeneic hematopoietic cell transplantation (allo-HCT) in chronic myelomonocytic leukemias (CMML), we assembled a retrospective cohort of CMML patients 18-70 years old diagnosed between 2000 and 2014 from an international CMML dataset (n = 730) and the EBMT registry (n = 384). The prognostic impact of allo-HCT was analyzed through univariable and multivariable time-dependent models and with a multistate model, accounting for age, sex, CMML prognostic scoring system (low or intermediate-1 grouped as lower-risk, intermediate-2 or high as higher-risk) at diagnosis, and AML transformation. In univariable analysis, lower-risk CMMLs had a 5-year overall survival (OS) of 20% with allo-HCT vs 42% without allo-HCT (P < .001). In higher-risk patients, 5-year OS was 27% with allo-HCT vs 15% without allo-HCT (P = .13). With multistate models, performing allo-HCT before AML transformation reduced OS in patients with lower-risk CMML, and a survival benefit was predicted for men with higher-risk CMML. In a multivariable analysis of lower-risk patients, performing allo-HCT before transformation to AML significantly increased the risk of death within 2 years of transplantation (hazard ratio [HR], 3.19; P < .001), with no significant change in long-term survival beyond this time point (HR, 0.98; P = .92). In higher-risk patients, allo-HCT significantly increased the risk of death in the first 2 years after transplant (HR 1.46; P = .01) but not beyond (HR, 0.60; P = .09). Performing allo-HCT before AML transformation decreases life expectancy in lower-risk patients but may be considered in higher-risk patients.

A predictive classifier of poor prognosis in transplanted patients with juvenile myelomonocytic leukemia: a study on behalf of the Société Francophone de Greffe de Moelle et de Thérapie Cellulaire.

Juvenile myelomonocytic leukemia (JMML) is an aggressive pediatric myeloproliferative neoplasm requiring hematopoietic stem cell transplantation (HSCT) in most cases. We retrospectively analyzed 119 JMML patients who underwent first allogeneic HSCT between 2002 and 2021. The majority (97%) carried a RAS-pathway mutation, and 62% exhibited karyotypic alterations or additional mutations in SETBP1, ASXL1, JAK3 and/or the RAS pathway. Relapse was the primary cause of death, with a 5-year cumulative incidence of 24.6% (95% CI: 17.1-32.9). Toxic deaths occurred in 12 patients, resulting in treatment-related mortality (TRM) of 9.0% (95% CI: 4.6-15.3). The 5-year overall (OS) and event-free survival were 73.6% (95% CI: 65.7-82.4) and 66.4% (95% CI: 58.2-75.8), respectively. Four independent adverse prognostic factors for OS were identified: age at diagnosis >2 years, time from diagnosis to HSCT ≥6 months, monocyte count at diagnosis >7.2x109/L, and the presence of additional genetic alterations. Based on these factors, we proposed a predictive classifier. Patients with 3 or more predictors (21% of the cohort) had a 5-year OS of 34.2%, whereas those with none (7%) had a 5-year OS of 100%. Our study demonstrates improved transplant outcomes compared to prior published data, which can be attributed to the synergistic impacts of a low TRM and a reduced, yet still substantial, relapse incidence. By integrating genetic information with clinical and hematologic features, we have devised a predictive classifier. This classifier effectively identifies a subgroup of patients who are at a heightened risk of unfavorable post-transplant outcomes who would benefit from novel therapeutic agents and post-transplant strategies.

Phenotypic profiling of CD34+ cells by advanced flow cytometry improves diagnosis of juvenile myelomonocytic leukemia.

Diagnostic criteria for juvenile myelomonocytic leukemia (JMML) are currently well defined, however in some patients diagnosis still remains a challenge. Flow cytometry is a well established tool for diagnosis and follow-up of hematological malignancies, nevertheless it is not routinely used for JMML diagnosis. Herewith, we characterized the CD34+ hematopoietic precursor cells collected from 31 children with JMML using a combination of standardized EuroFlow antibody panels to assess the ability to discriminate JMML cells from normal/reactive bone marrow cell as controls (n=29) or from cells of children with other hematological diseases mimicking JMML (n=9). CD34+ precursors in JMML showed markedly reduced B-cell and erythroid-committed precursors compared to controls, whereas monocytic and CD7+ lymphoid precursors were significantly expanded. Moreover, aberrant immunophenotypes were consistently present in CD34+ precursors in JMML, while they were virtually absent in controls. Multivariate logistic regression analysis showed that combined assessment of the number of CD34+CD7+ lymphoid precursors and CD34+ aberrant precursors or erythroid precursors had a great potential in discriminating JMMLs versus controls. Importantly our scoring model allowed highly efficient discrimination of truly JMML versus patients with JMML-like diseases. In conclusion, we show for the first time that CD34+ precursors from JMML patients display a unique immunophenotypic profile which might contribute to a fast and accurate diagnosis of JMML worldwide by applying an easy to standardize single eight-color antibody combination.

LNK/SH2B3 as a novel driver in juvenile myelomonocytic leukemia.

Mutations in five canonical Ras pathway genes (NF1, NRAS, KRAS, PTPN11 and CBL) are detected in nearly 90% of patients with juvenile myelomonocytic leukemia (JMML), a frequently fatal malignant neoplasm of early childhood. In this report, we describe seven patients diagnosed with SH2B3-mutated JMML, including five patients who were found to have initiating, loss-of-function mutations in the gene. SH2B3 encodes the adaptor protein LNK, a negative regulator of normal hematopoiesis upstream of the Ras pathway. These mutations were identified to be germline, somatic or a combination of both. Loss of function of LNK, which has been observed in other myeloid malignancies, results in abnormal proliferation of hematopoietic cells due to cytokine hypersensitivity and activation of the JAK/STAT signaling pathway. In vitro studies of induced pluripotent stem cell-derived JMML-like hematopoietic progenitor cells also demonstrated sensitivity of SH2B3-mutated hematopoietic progenitor cells to JAK inhibition. Lastly, we describe two patients with JMML and SH2B3 mutations who were treated with the JAK1/2 inhibitor ruxolitinib. This report expands the spectrum of initiating mutations in JMML and raises the possibility of targeting the JAK/STAT pathway in patients with SH2B3 mutations.

Noonan Syndrome-related Myeloproliferative Disorder Occurring in the Neonatal Period: Case Report and Literature Review.

Noonan syndrome-related myeloproliferative disorder (NS/MPD) and juvenile myelomonocytic leukemia (JMML) are rare MPDs that occur in young children. We herein report a case of NS/MPD with neonatal onset. The patient had a characteristic appearance and high monocyte count in the peripheral blood and bone marrow. Genetic testing showed the E139D mutation in PTPN11 ; however, the patient did not meet all the diagnostic criteria for JMML, and we thus diagnosed him with NS/MPD. Eight other cases of NS/MPD with neonatal onset are also summarized. The initial presentation varied, and the prognosis was considered poor compared with previous reports of NS/MPD.

Potential clinical use of azacitidine and MEK inhibitor combination therapy in PTPN11-mutated juvenile myelomonocytic leukemia.

Juvenile myelomonocytic leukemia (JMML) is a rare myeloproliferative neoplasm of childhood. The molecular hallmark of JMML is hyperactivation of the Ras/MAPK pathway with the most common cause being mutations in the gene PTPN11, encoding the protein tyrosine phosphatase SHP2. Current strategies for treating JMML include using the hypomethylating agent, 5-azacitidine (5-Aza) or MEK inhibitors trametinib and PD0325901 (PD-901), but none of these are curative as monotherapy. Utilizing an Shp2E76K/+ murine model of JMML, we show that the combination of 5-Aza and PD-901 modulates several hematologic abnormalities often seen in JMML patients, in part by reducing the burden of leukemic hematopoietic stem and progenitor cells (HSC/Ps). The reduced JMML features in drug-treated mice were associated with a decrease in p-MEK and p-ERK levels in Shp2E76K/+ mice treated with the combination of 5-Aza and PD-901. RNA-sequencing analysis revealed a reduction in several RAS and MAPK signaling-related genes. Additionally, a decrease in the expression of genes associated with inflammation and myeloid leukemia was also observed in Shp2E76K/+ mice treated with the combination of the two drugs. Finally, we report two patients with JMML and PTPN11 mutations treated with 5-Aza, trametinib, and chemotherapy who experienced a clinical response because of the combination treatment.

Therapeutic efficacy of RAS inhibitor trametinib using a juvenile myelomonocytic leukemia patient-derived xenograft model.

Juvenile myelomonocytic leukemia (JMML) is an aggressive pediatric leukemia with few effective treatments and poor outcomes even after stem cell transplantation, the only current curative treatment. We developed a JMML patient-derived xenograft (PDX) mouse model and demonstrated the in vivo therapeutic efficacy and confirmed the target of trametinib, a RAS-RAF-MEK-ERK pathway inhibitor, in this model. A PDX model was created through transplantation of patient JMML cells into mice, up to the second generation, and successful engraftment was confirmed using flow cytometry. JMML PDX mice were treated with trametinib versus vehicle control, with a median survival of 194 days in the treatment group versus 124 days in the control group (p = 0.02). Trametinib's target as a RAS pathway inhibitor was verified by showing inhibition of ERK phosphorylation using immunoblot assays. In conclusion, trametinib monotherapy significantly prolongs survival in our JMML PDX model by inhibiting the RAS pathway. Our model can be effectively used for assessment of novel targeted treatments, including potential combination therapies, to improve JMML outcomes.

Germline Neurofibromin 1 mutation enhances the anti-tumour immune response and decreases juvenile myelomonocytic leukaemia tumourigenicity.

Juvenile myelomonocytic leukaemia (JMML) is an aggressive paediatric leukaemia characterized by mutations in five canonical RAS pathway genes, including the NF1 gene. JMML is driven by germline NF1 gene mutations, with additional somatic aberrations resulting in the NF1 biallelic inactivation, leading to disease progression. Germline mutations in the NF1 gene alone primarily cause benign neurofibromatosis type 1 (NF1) tumours rather than malignant JMML, yet the underlying mechanism remains unclear. Here, we demonstrate that with reduced NF1 gene dose, immune cells are promoted in anti-tumour immune response. Comparing the biological properties of JMML and NF1 patients, we found that not only JMML but also NF1 patients driven by NF1 mutations could increase monocytes generation. But monocytes cannot further malignant development in NF1 patients. Utilizing haematopoietic and macrophage differentiation from iPSCs, we revealed that NF1 mutations or knockout (KO) recapitulated the classical haematopoietic pathological features of JMML with reduced NF1 gene dose. NF1 mutations or KO promoted the proliferation and immune function of NK cells and iMacs derived from iPSCs. Moreover, NF1-mutated iNKs had a high capacity to kill NF1-KO iMacs. NF1-mutated or KO iNKs administration delayed leukaemia progression in a xenograft animal model. Our findings demonstrate that germline NF1 mutations alone cannot directly drive JMML development and suggest a potential cell immunotherapy for JMML patients.

Immune dysregulation associated with co-occurring germline CBL and SH2B3 variants.

BACKGROUND: CBL syndrome is a RASopathy caused by heterozygous germline mutations of the Casitas B-lineage lymphoma (CBL) gene. It is characterized by heterogeneous clinical phenotype, including developmental delay, facial dysmorphisms, cardiovascular malformations and an increased risk of cancer development, particularly juvenile myelomonocytic leukemia (JMML). Although the clinical phenotype has been progressively defined in recent years, immunological manifestations have not been well elucidated to date. METHODS: We studied the genetic, immunological, coagulative, and clinical profile of a family with CBL syndrome that came to our observation after the diagnosis of JMML, with homozygous CBL mutation, in one of the members. RESULTS: Variant analysis revealed the co-occurrence of CBL heterozygous mutation (c.1141 T > C) and SH2B3 mutation (c.1697G > A) in two other members. Patients carrying both mutations showed an ALPS-like phenotype characterized by lymphoproliferation, cytopenia, increased double-negative T-cells, impaired Fas-mediated lymphocyte apoptosis, altered cell death in PBMC and low TRECs expression. A coagulative work-up was also performed and showed the presence of subclinical coagulative alterations in patients carrying both mutations. CONCLUSION: In the reported family, we described immune dysregulation, as part of the clinical spectrum of CBL mutation with the co-occurrence of SH2B3.

A nationwide survey of late effects in survivors of juvenile myelomonocytic leukemia in Japan.

We conducted a cross-sectional study using a questionnaire to explore the late effects in survivors of allogenic hematopoietic stem cell transplantation (HSCT) for juvenile myelomonocytic leukemia (JMML). The attending pediatric hematologists/oncologists completed the questionnaires. Of the 30 survivors, approximately 83% showed more than one late effect. The identified late effects included endocrine, dental, skin, ophthalmologic, musculoskeletal, pulmonary, neurocognitive, and cardiovascular dysfunction. The prevalence of short stature, pulmonary, cardiovascular, and nephrological complications was significantly elevated among survivors who were 12 years or more lapsed after HSCT. Therefore, a multidisciplinary follow-up system for survivors of JMML is crucial.

The Clinical Landscape of NRAS- mutated Juvenile Myelomonocytic Leukemia-like Myeloproliferation Includes Children With Costello Syndrome.

Juvenile myelomonocytic leukemia (JMML) is a rare, aggressive pediatric disorder characterized by pathologic myeloproliferation because of alterations in RAS pathway genes. NRAS -mutated JMML encompasses a broad range of clinical severity. Herein we describe 4 unique cases of NRAS -mutated JMML and JMML-like myeloproliferation, 2 with somatic mutations and 2 with germline mutations. These cases illustrate the diverse clinical and hematologic presentation of this subtype of JMML, including a very unusual example presenting with Auer rods. Lastly, this is the first report of patients with phenotypic Costello syndrome presenting with JMML-like myeloproliferation, highlighting an important clinical phenomenon that has not been previously described.

Inhibition of BTK and PI3Kδ impairs the development of human JMML stem and progenitor cells.

Juvenile myelomonocytic leukemia (JMML) is an aggressive myeloproliferative neoplasia that lacks effective targeted chemotherapies. Clinically, JMML manifests as monocytic leukocytosis, splenomegaly with consequential thrombocytopenia. Most commonly, patients have gain-of-function (GOF) oncogenic mutations in PTPN11 (SHP2), leading to Erk and Akt hyperactivation. Mechanism(s) involved in co-regulation of Erk and Akt in the context of GOF SHP2 are poorly understood. Here, we show that Bruton's tyrosine kinase (BTK) is hyperphosphorylated in GOF Shp2-bearing cells and utilizes B cell adaptor for PI3K to cooperate with p110δ, the catalytic subunit of PI3K. Dual inhibition of BTK and p110δ reduces the activation of both Erk and Akt. In vivo, individual targeting of BTK or p110δ in a mouse model of human JMML equally reduces monocytosis and splenomegaly; however, the combined treatment results in a more robust inhibition and uniquely rescues anemia and thrombocytopenia. RNA-seq analysis of drug-treated mice showed a profound reduction in the expression of genes associated with leukemic cell migration and inflammation, leading to correction in the infiltration of leukemic cells in the lung, liver, and spleen. Remarkably, in a patient derived xenograft model of JMML, leukemia-initiating stem and progenitor cells were potently inhibited in response to the dual drug treatment.

Transient immune deficiency accompanied with homozygous CBL rare variant.

BACKGROUND: A critical role in cellular proliferation is played by Casitas B-lineage Lymphoma proto-oncogene (CBL). Germline heterozygous CBL variants give rise to CBL syndrome, which is phenotypically similar to RASopathy. Somatic mutations in CBL have been reported in patients with juvenile myelomonocytic leukemia (JMML). METHODS: Exome analysis was performed in a patient with immunodeficiency who developed Pneumocystis jirovecii pneumonia. RESULTS: Exome analysis identified a homozygous CBL missense variant. Cell biological analysis of this CBL variant confirmed attenuated function. CONCLUSION: Spontaneous regression of hematological proliferation has been observed in patients with CBL-mutated JMML and in patients with CBL syndrome. Intriguingly, immunological impairment was spontaneously ameliorated by aging in this patient.

[Successful second allogeneic hematopoietic stem cell transplantation with azacitidine as bridging therapy for relapsed juvenile myelomonocytic leukemia].

Hematopoietic cell transplantation (HCT) is the only curative therapy for juvenile myelomonocytic leukemia (JMML). Meanwhile, an established conventional chemotherapy before HCT remains unavailable. Studies have shown that azacitidine (AZA), which is a DNA methyltransferase inhibitor, is clinically effective for JMML as a bridging therapy for HCT; a prospective clinical trial in Japan is ongoing. Herein, we present a case of a patient with JMML who was administered AZA as bridging therapy for both first and second HCT. A 3-year-old boy with neurofibromatosis type 1 was administered with intravenous AZA (75 mg/m2/day for 7 days, intervals of 28 days, and four cycles) and received myeloablative HCT (unrelated bone marrow). When relapse occurred on day 123, four additional AZA therapy cycles were administered, and the patient received a second nonmyeloablative HCT (cord blood). After seven AZA therapy cycles as post HCT consolidation, hematological remission was sustained for 16 months after the second HCT. No severe adverse events occurred. AZA is effective for JMML as a bridging therapy for HCT and has robust cytoreductive potential despite the risk of relapse.

[Clinical features and prognosis of juvenile myelomonocytic leukemia: an analysis of 63 cases]. / 63ä¾‹å¹¼å¹´åž‹ç²’å•æ ¸ç»†èƒžç™½è¡€ç— çš„ä¸´åºŠç‰¹å¾ä¸Žé¢„åŽåˆ†æž.

OBJECTIVES: To investigate the clinical features of juvenile myelomonocytic leukemia (JMML) and their association with prognosis. METHODS: Clinical and prognosis data were collected from the children with JMML who were admitted from January 2008 to December 2016, and the influencing factors for prognosis were analyzed. RESULTS: A total of 63 children with JMML were included, with a median age of onset of 25 months and a male/female ratio of 3.2∶1. JMML genetic testing was performed for 54 children, and PTPN11 mutation was the most common mutation and was observed in 23 children (43%), among whom 19 had PTPN11 mutation alone and 4 had compound PTPN11 mutation, followed by NRAS mutation observed in 14 children (26%), among whom 12 had NRAS mutation alone and 2 had compound NRAS mutation. The 5-year overall survival (OS) rate was only 22%±10% in these children with JMML. Of the 63 children, 13 (21%) underwent hematopoietic stem cell transplantation (HSCT). The HSCT group had a significantly higher 5-year OS rate than the non-HSCT group (46%±14% vs 29%±7%, P<0.05). There was no significant difference in the 5-year OS rate between the children without PTPN11 gene mutation and those with PTPN11 gene mutation (30%±14% vs 27%±10%, P>0.05). The Cox proportional-hazards regression model analysis showed that platelet count <40×109/L at diagnosis was an influencing factor for 5-year OS rate in children with JMML (P<0.05). CONCLUSIONS: The PTPN11 gene was the most common mutant gene in JMML. Platelet count at diagnosis is associated with the prognosis in children with JMML. HSCT can improve the prognosis of children with JMML.

Immunophenotypic changes in juvenile myelomonocytic leukaemia after treatment with hypomethylating agent: Do they help to evaluate dept of response?

5-Azacitidine has been used before stem cell transplantation in juvenile myelomonocytic leukaemia (JMML) patients. Recently, we have described immunophenotypic features in JMML at diagnosis. Here, our aim was to examine the changes in the immunophenotypic features during azacitidine treatment, correlating it with clinical response. Patients treated with 5-azacitidine were evaluated at diagnosis and after three and six cycles of medication. Among 32 patients entering the study, 28 patients were examined after three cycles and 25 patients after six. Patients showed a reduction in CD34/CD117+ cells: median 3.35% at diagnosis, 2.8% after three cycles and 1.63% after six. B-cell progenitors were decreased at diagnosis and decreased after treatment. Monocytes decreased: 11.91% to 6.4% and 4.18% respectively. Complete response was associated with increase in classical monocytes. T lymphocytes, reduced at diagnosis, increased in patients responding to 5-azacitidine. Immunophenotypic aberrancies including expression of CD7 in myeloid progenitors remained after treatment. This feature was associated with a worse response to treatment, as well as presence of NF1. Immunophenotyping was feasible in all patients. Clinical response was associated with a decrease of myeloid progenitors and monocytes and a rise in T lymphocytes although phenotypic aberrancies persisted. The largest effect was observed after three cycles.

Molecular and phenotypic diversity of CBL-mutated juvenile myelomonocytic leukemia.

Mutations in the gene CBL were first identified in adults with various myeloid malignancies. Some patients with juvenile myelomonocytic leukemia (JMML) were also noted to harbor mutations in CBL, but were found to have generally less aggressive disease courses compared to other forms of Ras pathway-mutant JMML. Importantly, and in contrast to most reports in adults, the majority of CBL mutations in JMML patients are germline with acquired uniparental disomy occurring in affected marrow cells. Here, we systematically studied a large cohort of 33 JMML patients with CBL mutations and found this disease to be highly diverse in presentation and overall outcome. Moreover, we discovered somatically-acquired CBL mutations in 15% of pediatric patients who presented with more aggressive disease. Neither clinical features nor methylation profiling were able to distinguish somatic CBL patients from germline CBL patients, highlighting the need for germline testing. Overall, we demonstrate that disease courses are quite heterogeneous even among germline CBL patients. Prospective clinical trials are warranted to find ideal treatment strategies for this diverse cohort of patients.

How I diagnose and treat chronic myelomonocytic leukemia.

Chronic myelomonocytic leukemia (CMML) is a myelodysplastic syndrome/myeloproliferative overlap neoplasm characterized by sustained peripheral blood monocytosis and an inherent risk for transformation to acute myeloid leukemia (15-30% over 3-5 years). While CMML is morphologically classified into CMML-0, 1 and 2 based on peripheral blood and bone marrow promonocyte/blast counts, a more clinically relevant classification into dysplastic and proliferative subtypes, based on the presenting white blood cell count, is helpful in prognostication and therapeutics. CMML is a neoplasm associated with aging, occurring on the background of clonal hematopoiesis, with TET2 and SRSF2 mutations being early initiating events. The subsequent acquisitions of ASXL1, RUNX1, SF3B1 and DNMT3A mutations usually give rise to dysplastic CMML, while ASXL1, JAK2V617F and RAS pathway mutations give rise to proliferative CMML. Patients with proliferative CMML have a more aggressive course with higher rates of transformation to acute myeloid leukemia. Allogeneic stem cell transplant remains the only potential cure for CMML; however, given the advanced median age at presentation (73 years) and comorbidities, it is an option for only a few affected patients (10%). While DNA methyltransferase inhibitors are approved for the management of CMML, the overall response rates are 40-50%, with true complete remission rates of <20%. These agents seem to be particularly ineffective in proliferative CMML subtypes with RAS mutations, while the TET2mutant/ASXL1wildtype genotype seems to be the best predictor for responses. These agents epigenetically restore hematopoiesis in responding patients without altering mutational allele burdens and progression remains inevitable. Rationally derived personalized/targeted therapies with disease-modifying capabilities are much needed.