PB1891: VARIANT PHILADELPHIA CHROMOSOME IN CML

Abstract

Background: Chronic myeloid leukemia is a clonal malignant disorder of a pluripotent hematopoietic stem cell characterized by the Philadelphia chromosome and the reciprocal translocation t(9:22)(q34;q11). Almost 5 to 10 percent of chronic myeloid leukemia cases demonstrate variant Philadelphia translocations. Aims: To contribute to the description of patients’ clinical characteristics and prognosis with variant Ph chromosome-positive leukemia, we report a Ph chromosome-positive CML in the chronic phase characterized by an unusual variant Ph chromosome. Methods: An elderly male Libyan patient was suspected to have chronic myeloid leukemia. Cytogenetic and molecular exploration were conducted using bone marrow and blood samples. Cytogenetic analysis was performed on lymphocytes and bone marrow cells after short-term culture (48 hours). The cells were treated with colchicine and hypotonic KCl solution. The pellet was fixed and washed in methanol-acetic acid (3:1). The cells were resuspended in fixative and dropped onto slides. Chromosome-banding analysis was performed using RHG and GTG banding techniques. Three karyotypes and 25 metaphases were analyzed according to the International System for Human Cytogenetic Nomenclature. Multiplex reverse transcription-PCR (RT-PCR) was used to identify the BCR-ABL1 transcript. RT-PCR was performed according to European recommendations, as described previously. Results: Clinical assessment confirmed the first chronic phase of a chronic myeloid leukemia. Chromosomal formula showed an homogeneous structural translocation: t(1;9;12;22)(p35-36;q34;p13;q11) involving four chromosomal regions, 1p35-36, 9q34, 12p13 and 22q11.2. Molecular investigation confirmed the Ph nature of the chromosomal abnormality by showing the BCR-ABL1 transcript. The patient was treated by using Imatinib molecule with a favorable therapeutic response. Summary/Conclusion: A new variant Ph chromosome-positive CML in the chronic phase is reported. It is a four-way Ph translocation t(1;9;12;22)(p35-36;q34;p13;q11) involving four chromosomal regions, 1p35-36, 9q34, 12p13 and 22q11.2. Imatinib, the first-generation TKI treatment was efficient.