What is the gene fusion involved in the chromosomal abnormality found in Acute Promyelocytic Leukemia (APL)?

In Acute Promyelocytic Leukemia (APL), the characteristic chromosomal abnormality involves a fusion gene known as PML/RARA. This fusion occurs due to a translocation, specifically t(15;17), which combines the promyelocytic leukemia (PML) gene located on chromosome 15 with the retinoic acid receptor alpha (RARA) gene found on chromosome 17.

The resulting PML/RARA fusion protein plays a critical role in the pathogenesis of APL by interfering with normal myeloid differentiation and promoting the accumulation of promyelocytes. This abnormal protein effectively inhibits the transcription of genes necessary for hematopoietic differentiation, leading to the characteristic clinical manifestations of APL, such as coagulopathy and the presence of promyelocytes with heavy granulation in the bone marrow.

In contrast, the other choices are associated with different types of leukemias or hematological disorders and are not specifically related to APL:

• BCR/ABL is linked with Chronic Myeloid Leukemia (CML) due to a different translocation involving the BCR gene on chromosome 22 and the ABL gene on chromosome 9.
• FGFR1/FIP1L1 fusion is associated with