The PRKAR1A gene is fused to RARA in a new variant acute promyelocytic leukemia

We report the molecular and cytogenetic characterization of a novel variant of acute promyelocytic leukemia (APL). The bone marrow showed 88% hypergranular promyelocytes, and the karyotype was 47,XY,+22 [5]/46,XY[30]. Fluorescence in situ hybridization (FISH) indicated disruption and deletion of the 5'-end of the RARA gene. Treatment with all-trans retinoic acid, idarubicin, and arsenic trioxide induced cytogenetic complete remission without morphologic evidence of residual leukemia. The diagnostic marrow was negative for PML-RARA transcripts by reverse transcription-polymerase chain reaction (RT-PCR), but an atypical product was observed. Sequencing showed partial homology to the PRKAR1A gene, encoding the regulatory subunit type I-alpha of cyclic adenosine monophosphate-dependent protein kinase. RT-PCR using specific primers for PRKAR1A and RARA amplified 2 transcript splice variants of a PRKAR1A-RARA fusion gene, and PRKAR1A and RARA FISH probes confirmed the fusion. This novel PRKAR1A-RARA gene rearrangement is the fifth variant APL in which the RARA partner gene has been identified and the second known rearrangement of PRKAR1A in a malignant disease. This trial was registered at www.actr.org.au with the Australian Clinical Trials Registry as number 12605000070639.