5'RARA submicroscopic deletion from new variant translocation involving chromosomes 15, 17, and 18, in a case of acute promyelocytic leukemia

Submicroscopic deletions of the PML-RARA fusion genes constitute rare rearrangements in acute promyelocytic leukemia (APL). We describe a rare case of APL carrying a novel complex translocation involving chromosomes 15, 17, and 18 associated with a submicroscopic deletion of the 5' part of the RARA gene, as evidenced by fluorescence in situ hybridization (FISH). A PML/RARA dual-fusion probe did not reveal the RARA-PML fusion signal on the der(17q), usually detected in the typical t(15;17). The RARA break-apart probe showed a deletion hybridization pattern with loss of the signal corresponding to the 5' portion of the RARA gene. Reverse transcriptase-polymerase chain reaction confirmed the absence of the fusion RARA-PML transcript. The patient achieved complete remission, but died during consolidation therapy, 2 months after diagnosis. To our knowledge, this is the first reported case of APL with a complex variant t(15;17) involving chromosome 18 at band q12 and one of the very rare described cases displaying a submicroscopic deletion of the RARA 5' region. Further cases are needed to delineate the incidence of submicroscopic deletions in APL and elucidate their prognostic impact.