Case Report: Co-existence of a novel EXOC4-TRHDE gene fusion with PML-RARA in acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) is a type of myeloid leukemia with a specific chromosomal translocation t(15;17)(q22; q12) forming the PML-RARA fusion gene. However, approximately one third of newly diagnosed patients with APL have additional chromosomal abnormalities. Here, we report a case of APL with co-existence of a novel translocation t(7;12)(q32;q13) involving an out-of-frame fusion between EXOC4 and TRHDE, together with PML-RARA. The patient achieved complete remission after treatment with conventional therapy with all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). Although the causative link between EXOC4-TRHDE and PML-RARA has yet to be established, the patient had a good response to therapy, suggesting that the EXOC4-TRHDE fusion does not affect the efficacy of combined treatment with ATRA and ATO.