Chronic myeloid leukemia

Last revised by Joshua Yap on 7 Sep 2022

Chronic myeloid leukemia (CML), also known as chronic myelogenous leukemia, is a myeloproliferative neoplasm characterized by the overproduction of granulocytes with fairly normal differentiation.

The annual incidence is about 1 per 100,000 1,3. The typical age at presentation is 50-60 years 1. Exposure to high-dose radiation is a risk factor 3.

Constitutional symptoms are common, such as fatigue, weight loss, and sweats 2. Some patients are asymptomatic, with the diagnosis being first suspected based upon routine blood work finding leukocytosis with a predominance of the neutrophil lineage.

Chronic myeloid leukemia is caused by a chromosomal abnormality in hematopoietic stem cells in which reciprocal translocation between chromosomes 9 and 22 creates the fusion gene BCR-ABL1. The shortened chromosome 22 containing the fusion gene is called the Philadelphia chromosome. The diagnosis is established by karyotype (to detect the Philadelphia chromosome), fluorescence in situ hybridization (to detect the BCR-ABL1 fusion gene), or reverse transcription-polymerase chain reaction (to detect the BCR-ABL1 mRNA product).

Patients commonly have splenomegaly and diffuse marrow infiltration (manifests as abnormally low signal on T1-weighted MRI).

First-line medical therapy consists of tyrosine kinase inhibitors (TKI), e.g. imatinib, dasatinib, or nilotinib 1,3. With tyrosine kinase inhibitor treatment, life expectancy approaches that of the general population.

In some treated patients and in untreated patients, the disease progresses over several years through an accelerated phase and culminates in a blast phase (or blast crisis), which represents fatal acute leukemia.

For those patients that have progressed to the accelerated or blast phases despite treatment with tyrosine kinase inhibitors, guidelines recommend replacement with an alternative tyrosine kinase inhibitor while waiting for hematopoietic stem cell transplantation 3

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