Disease Overview: Chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic stem cell disorder that is classified as a myelodysplastic/myeloproliferative neoplasm by the 2008 World Health Organization classification of hematopoietic tumors. It is characterized by absolute monocytosis (>1 × 10 9 L -1) in the peripheral blood that persists for at least 3 months. Patients may present with symptoms related to cytopenias and/or an underlying hypercatabolic state with drenching night sweats, splenomegaly, and weight loss. Diagnosis: The diagnosis of CMML rests on a combination of morphologic, histopathologic, and chromosomal abnormalities in the bone marrow, after careful exclusion of other conditions (both malignant and nonmalignant) that can cause monocytosis. Numerous molecular abnormalities have been recently recognized in patients with CMML-unfortunately, no single pathognomonic finding specific to CMML has been identified thus far. Risk stratification: The International Prognostic Scoring System for myelodysplastic syndrome (MDS) cannot be used to risk stratify patients with CMML because this model excluded patients with a leukocyte count >12 × 10 9 L -1. Other risk stratification models such as the MD Anderson prognostic score and Dusseldorf score have been published. In the only model that took karyotype into account, bone marrow blasts ≥ 10%, leukocyte count ≥ 13 × 10 9 L -1, hemoglobin < 10 g/dL, platelet count < 100 × 10 9 L -1, and presence of trisomy 8, abnormalities of chromosome 7, or complex karyotype were found to be independent predictors of adverse survival. Risk-adapted therapy: The Food and Drug Administration has approved azacitidine and decitabine for the treatment of patients with CMML based on two pivotal trials in MDS. Novel classes of agents including immunomodulatory drugs, nucleoside analogs, and small-molecule tyrosine kinase inhibitors are being investigated in the treatment of CMML. With the advent of reduced intensity conditioning, an allogeneic stem cell transplant has also become a viable option for a subset of patients.
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