A case of acute myeloid leukemia with Major-BCR::ABL1 [e14 (b3) a3 type], which could not be detected by RT-qPCR method

Abstract

We report a case of acute myeloid leukemia with Major-BCR::ABL1, which could not be detected by RT-qPCR method. The patient was a male in his 70s. He was diagnosed as acute myeloid leukemia because of the finding of leukocytosis and 37% blast-like cells in the peripheral blood and 26.6% in the bone marrow. In the bone marrow, we conducted RT-qPCR as a screening method for chimeric gene, including Major-BCR::ABL1 which commonly found in leukemia patients. Although no chimeric gene was detected by RT-qPCR, cytogenetics and FISH indicated the existence of BCR::ABL1. Later, detail investigation revealed that the fusion gene in this case was the Major-BCR::ABL1 [e14 (b3) a3 type], in which the ABL1 has a rare cleavage point. In addition, we built a new method based on RT-qPCR for measuring Major-BCR::ABL1 [e14 (b3) a3 type]. New method enables us to detect not only a2 type Major-BCR::ABL1 but also a3 type Major-BCR::ABL1. We will adapt the new method as a screening for patients suspected with leukemia, especially at the first onset.