RARA and acute promyelocytic leukemia: The genetic cause of APL phenotype is due to a balanced reciprocal chromosomal translocation t(15;17) which occurs in 100% of APL cases and produces an anomalous fusion protein known as Promyelocytic leukemia protein (PML) - Retinoic Acid Receptor Alpha (RARα) (PML-RARα)4,5.