Central nervous system relapse in CD56+, FLT3/ITD+ promyelocytic leukemia

Central nervous system (CNS) involvement in acute promyelocytic leukemia (APL) is rare and tends to be seen mostly following treatment with all-trans retinoic acid (ATRA), due to prolonged patient survival and poor penetration of the drug in the CNS. At least 10% of extramedullary relapses in APL involve the CNS, and associated factors include an increased age, the BCR isoform, the development of differentiation syndrome, a high white cell count at presentation and hemorrhage into the CNS during induction therapy. We present the case of a patient with high-risk APL, CD56+, CD2+ in whom a CNS relapse was diagnosed through the presence of a PML/RARα rearrangement on PCR of the cerebrospinal fluid (CSF).