Novel PML-RARA Fusion Gene on Chromosome 17 in Acute Promyelocytic Leukemia with Normal Chromosome 15 and 17

ABSTRACT

We describe a patient with acute promyelocytic leukemia (APL) with no detectable cytogenetic abnormality of either chromosomes 15 or 17 who nevertheless had juxtaposition of promyelocytic leukemia (PML) and retinoic acid receptor-alpha (RARA) and expressed a chimeric transcript. Conventional cytogenetics showed the 46, XX. The metaphase fluorescence in situ hybridization (FISH) with a 5' PML and 3' RARA probe showed a juxtaposed PML-RARA fusion signal on one chromosome 17 homologue, an RARA signals on the other chromosome 17 homologue, and one PML signal on each chromosome 15 homologue. Our patient is presently in remission and doing well after chemotherapy with idarubicin and all trans retinoic acid (ATRA) treatment. Our results show that APL patients with cytogenetically normal chromosome 15 and 17 may, nevertheless, have involvement of both PML and RARA genes and as the prognostic outcome in APL is associated with the presence of a PML-RARA fusion, it is necessary to perform RT-PCR or FISH to aid diagnosis.