**2. Acute myeloid leukemia (AML)**

AML is a complex malignancy characterized by a high heterogeneity of aberrant myeloid precursors. In addition to family history of hematologic disorders and exposure to environmental factors, aging increases the incidence of AML. Although AML arises from transformed hematopoietic stem cells, the etiology of this form of leukemia remains mostly

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

unidentified. However, we know that consecutive genomic mutations and epigenetic modifications lead to the progression of the disease. Alterations in important genes have been characterized leading to the development of novel targeted therapeutic strategies. However, significant variations in the genetic and the epigenetic of AML are found among patients. Thus, development of efficient treatment of AML remains a significant clinical challenge.

**4. Chronic myelomonocytic leukemia (CMML)**

**5. Juvenile myelomonocytic leukemia (JMML)**

**6. Atypical chronic myeloid leukemia (aCML)**

therapy for JMML.

**(MDS/MPN-UC)**

with imatinib mesylate.

**8. Conclusion**

plantation or stem cell transplantation appears to be more effective.

CMML displays irregular features, varying from myelodysplastic to myeloproliferative. The majority of CMML patients show persistent somatic mutations. Around 15% of CMML can evolve to AML, and when this transition occurs, a poor prognosis is predicted. Many chemotherapy regimens for CMML have been used with only limited success. Bone marrow trans-

Introductory Chapter: Myeloid Leukemia http://dx.doi.org/10.5772/intechopen.73858 5

JMML is a rare myeloid disorder of childhood. Although the etiology of JMML is not known, children with neurofibromatosis type 1 (NF1) have high risk for developing JMML. Children diagnostic at 2 years old and up have a poorer prognosis. Thrombopenia and a high HbF level have also been associated with a poor prognosis. Currently, BMT appears to be the best

aCML is a very rare myeloid leukemia, mainly occurring in elderly people. This disorder displays both MDS and CMPD features. aCML seems to respond poorly to interferon alpha

MDS/MPN-UC is also called mixed myeloproliferative/myelodysplastic syndrome. Since it shows both MDS/MPN features and not meeting the criteria of the described MDS/MPN categories, this disorder is unclassifiable. A mutation on Jak2 kinase causing its constitutive activation might be involved in the disease at least in some MDS/MPN-UC patients. Adult patients with platelet-derived growth factor receptor gene rearrangements might be treated

Important progress in both the diagnosis and the treatment of myeloid leukemia has been realized. Currently, many treatments are proposed. In CML tremendous success has been achieved with TKI therapy. However, important challenges remain for establishing more focused therapies and determining useful biomarkers associated with the resistance or the success to therapy.

therapy. However, treatment with hydroxyurea may lead to a limited remission.

**7. Myelodysplastic/myeloproliferative neoplasm-unclassifiable** 

Current AML treatment is generally based on classical chemotherapy, targeted therapy, and stem cell transplantation. The emergence of personalized medicine is still underway. Optimal biological information leading to patient selection and individual therapy are uncommon.

In addition to the age of AML patients, cytogenetics of the tumor and clinical appreciations are fundamental for the prognosis and the success of the treatment. Promyelocytic leukemia is the subset of AML with the highest proportion of cure rate. Patients are benefiting from targeted therapy such as all-transretinoic acid treatment. Currently, several other targeted therapies are available.

The limiting parameters for AML targeted therapy are the tumor heterogeneity and its variability during the course of disease and therapy, resulting in unpredictable response, and constitute the current challenge for establishing successful personalized therapeutic regimens.
