5q- Syndrome in Transformation to the Philadelphia Chromosome Positive Acute Myeloblastic Leukemia

Background: A rare 5q- syndrome subtype (OMIM:153550) of the myelodysplastic syndrome (MDS) evolved to the Philadelphia (Ph) chromosome positive acute myeloblastic leukemia (AML) is presented. The MDS is an acquired clonal stem cell disorder frequently associated with a variety of chromosomal abnormalities. The most common karyotype abnormalities in MDS are del(5q), -7 and +8. The t(9;22)(q34;q11) results in the formation of the Ph chromosome and generates an active chimerical BCR-ABL tyrosine kinase most commonly associated with chronic myelogenous leukemia (CML) and adult precursor B-acute lymphoblastic leukemia (B-ALL). The Ph chromosome positive MDS and AML are uncommon with only 1-2% of newly diagnosed cases. Case report: We present a 72-year old woman with MDS. The HG-banding technique applied on unstimulated bone marrow cells showed 46,XX,del(5)(q13q33)[10]/46,XX. Ten months later, the white blood cell (WBC) count increased to 72×109/l, with 60% of myeloblasts in the formula. The bone marrow aspirate was hypercellular with 50% blasts. The cytogenetic study demonstrated the presence of Ph chromosome together with the initial del(5q) in the same cellular clone. Chemotherapy with hydroxyurea and low-dose cytosine arabinoside was followed by an increase in WBC count to 98×109/l. The dosage of cytosine arabinoside was escalated to 100 mg/m2, for 7 days resulting in a drop in the WBC count to 12×109/l. The follow-up bone marrow aspirations showed a further progression of disease with >70% of myeloblasts in the myelogram. The patient lived 10 months after the initial diagnosis of MDS was made and another 4 months after the diagnosis of secondary AML. Conclusion: The karyotype evolution from the solely 5q- to the 5q- and Ph-positive clone in the MDS in transformation to secondary AML (sAML) is a rare event. To our knowledge, this is a second such case reported in the literature. Based on current literature, we discuss possible links between the 5q- syndrome, BCR/ABL-negative chronic myeloproliferative neoplasms and the BCR/ABL-positive leukemias.