Why would I be BCR-ABL positive and Philadelphia chromosome negative?

Question

Hello doctor,

Can you please explain why I would have the gene and not the chromosome? Ph-negative, BCR-ABL-positive CML. The labs pointed to this. I had bone marrow aspiration and biopsy. I saw the doctor again. From all the labs, it looks like there is CD4 and CD8 elevated ratio 16.5, 8 % NK, lymphocytes 4 %, 1 % polyclonal B cells, 90 % mature T cells, no CD 34 granulocytosis. PBS shows increased granulocytes. Flow the differential diagnosis includes a reactive granulocytosis or a myeloproliferative IE CML. BCR/ABL translocation in 18 % of the cells on FISH 36/200.My report is attached.

Answer 1

Hello,

Welcome to icliniq.com.

Chronic myeloid leukemia (CML) is a hematopoietic disorder, almost always characterized by the presence of the Philadelphia chromosome (Ph), usually due to t(9;22)(q34;q11) or its variants. The Ph results in the formation of the BCR/ABL1 fusion gene, which is a constitutively activated tyrosine kinase.

Around 1 % of CML patients appear to have a Ph-negative karyotype but carry a cryptic BCR/ABL1 fusion that can be located by fluorescence in situ hybridization (FISH) at chromosome 22q11, 9q34 or a third chromosome. Hence, the cytogenetic profile is normal by karyotyping in Ph-negative patients but they have the BCR/ABL fusion gene which is detected by molecular methods like FISH and PCR.