Chronic myelogenous leukemia (CML) accounts for 15-20% of adult leukemias but is 
very rare in children (2%). Fewer than 10% of CML patients are younger than 20 
years. CML is a myeloproliferative disorder characterized by the presence of the 
Philadelphia chromosome or the BCR-ABL fusion oncogene. The objective of this 
paper is to present the monitoring of imatinib therapy in two children with CML 
by the BCR-ABL fusion gene expression assessment from peripheral blood with 
quantitative real-time polymerase chain reaction (PCR) method.
PATIENTS AND METHODS: The 18 and six months follow-up of the patients included 
clinical examination, routine laboratory tests, bone marrow aspirate 
investigation including cytogenetic tests and the major BCR-ABL fusion gene 
expression measurement with qRT-PCR method from the peripheral blood.
RESULTS: Patient No. 1 diagnosed with chronic phase CML showed excellent 
adherence to daily 400 mg imatinib treatment and achieved complete hematologic 
(CHR) and cytogenetic response (CCR) by three months and major molecular 
response (MMR) by 12 months, with lack of side effects due to imatinib. Patient 
No. 2 experienced severe hematologic toxicity, which necessitated temporary 
withdrawal of the drug. Transient non-compliance together with imatinib dose 
reduction has driven to treatment failure. In this case, mutational analysis is 
warranted.
CONCLUSIONS: BCR-ABL fusion gene expression level measurement from peripheral 
blood with qRT-PCR method is an excellent tool in the follow-up of CML patients.