A three way complex translocation (4; 9; 22) in two patients with chronic myelocytic leukemia.

ABSTRACT

Chronic myeloid leukemia (CML) is genetically characterized by the reciprocal translocation of chromosome 9 and 22, t(9;22)(q34;q11) which results in the fusion of BCR/ABL gene observed on the derivative chromosome 22 called Philadelphia (Ph') chromosome. About 5-8% of Philadelphia positive patients with CML show various complex translocations involving third chromosome in addition to chromosome 9 and 22. In present report we discuss two cases with CML referred at our centre. At the time of initial diagnosis and after 9 months of treatment, one of the patients showed 100% presence of Philadelphia positive in bone marrow culture. During follow-up in an accelerated state, his cytogenetic study revealed a complex translocation (4;9;22)(q25;q34;q11) along with an additional Philadelphia and marker chromosome. The second patient showed a complex (4;9;22)(q25;q34;q11) translocation at the time of diagnosis. He was on hydroxyurea and his follow-up cytogenetic study after the course of chemotherapy showed no changes. Further confirmation of complex translocation was done by FISH study using bcr/abl and whole chromosome 9 probes. Though the additional genes involved in complex variant Ph' rearrangements have not been characterized, both patients are healthy till 3 to 5 years of initial diagnosis. This could be attributed to the benign effect resulted from reciprocal translocation with no loss or gain of the genetic material.