Isolated Central Nervous System Infiltrated and Progressed to Acute Myeloid Leukemia from Chronic Myeloid Leukemia with e1a3 BCR-ABL1 Transcript: A Rare Case Report and Literature Review

The chronic myeloid leukemia (CML) is easily diagnosed by laboratory examination, however, rare BCR-ABL1 mRNA transcripts variants, such as e1a3 present diagnosis and therapeutic challenges. This case report details the diagnosis and management of a CML patient with the e1a3 transcript by FISH and RT-PCR. Following initial diagnosis, the patient was treated with the tyrosine kinase inhibitor (TKI) Flumatinib. During the treatment, although the FCM-MRD of the bone marrow kept negative, the e1a3 expression detected by PCR always remained positive. After eighteen months, the patient experienced headaches, vomiting, and blurred vision. Subsequent bone marrow analysis and flow cytometry detection of cerebrospinal fluid indicated that the patient had entered the blast phase, progressing to acute myeloid leukemia (AML). Treatment was switched to the third-generation TKI olverembatinib, combined with chemotherapy, followed by allogeneic hematopoietic stem cell transplantation. The patient remains disease-free following olverembatinib maintenance therapy. This case underscores the importance of comprehensive diagnostic apporsches and the potential efficacy of third-generation TKIs and allo-HSCT in the treatment of e1a3-type CML.