RARA and RARG Gene Downregulation Associated with EZH2 Mutation in Acute Promyelocytic-Like Morphology Leukemia

Most Acute Promyelocytic Leukemia (APL) patients express PML-RARA fusion; in rare cases RARA is rearranged with partner genes other than PML. To date, only two patients presenting features similar to APL showing the RARG gene rearrangement have been described. We report an Acute Myeloid Leukemia (AML) patient with morphology resembling APL without involvement of the RARA gene. Molecular and Fluorescent In Situ Hybridization (FISH) analyses excluded PML-RARA fusion and variant rearrangements involving RARA and RARG loci. Targeted Next Generation Sequencing showed EZH2-D185H mutation. As this mutation involved the region of interaction with DNA methyltransferases, we speculate an epigenetic alteration of genes involved in the APL-like phenotype. Expression analysis by droplet digital Polymerase Chain Reaction (PCR) revealed downregulation of the RARA and RARG genes. We hypothesize a novel mechanism of EZH2 function alteration, which may be responsible for an AML with APL-like phenotype featuring dysregulation of the RARA and RARG genes.