Pediatric chronic myeloid leukemia with a BCR- FIBCD1-ABL1 fusion transcript: a case report and literature review

Objective: To analyze the genetic phenotype of a pediatric chronic phase chronic myeloid leukemia(CML-CP) patient with a rare BCR-ABL1 fusion transcript and evaluate the therapeutic effect of tyrosine kinase inhibitor (TKI), also we review the reported cases in the databases to explore the treatment and prognosis in chronic myeloid leukemia with e8a2 BCR-ABL1 fusion gene. Methods: A 3-year-old girl was diagnosed with CML-CP in our hospital，the laboratory results and treatment were analyzed. Treatment and response to TKI inhibitors in the CML-CP patients presented with a novel e8a2 fusion gene were reviewed by searching the databases of pubmed and wanfang. Results: The patient was admitted to our hospital due to skin ecchymosis and cervical lymph node swelling，and was diagnosed as CML by bone marrow cell morphology, but P190, P210 and P230 were negative in peripheral blood and bone marrow examination. BCR (e8) -FIBCD1-ABL1 (a2) fusion gene was positive in peripheral blood by Nested RT-PCR. A total of 26 CML patients with e8a2 BCR-ABL1 fusion transcript in the database were reviewed, all of which were adult cases. In the literature, 21 patients received TKI inhibitor treatment, 19/21 (90.4%) achieved different degrees of molecular response. This case onset with elevated white blood cells and thrombocytopenia,and after imatinib treatment， the patient had achieved complete hematologic remission, and the BCR-ABL1 fusion gene transcript could not be detected. However, the bone marrow chromosomes showed a complex karyotype of 38-40,XX,-7,-17,-20,-21,-22[cp7] /46,XX at the follow-up of 39 months. Conclusions: CMI-CP with e8a2 BCR-ABL1 genotype is rare, we first report this atypical e8a2 BCR-ABL1 transcript expression in pediatric CML patient. Although complete hematological remission continued after TKI inhibitor treatment, an abnormal karyotype was found in bone marrow chromosomes, suggesting that this variant genotype may have a poor prognosis, and following up closely is necessary.